Open up your mind and say, ahh...

When sitting down for a job interview at a top U.S. tech company, you’d typically expect the interviewer to hammer you with questions testing your abilities, past history and knowledge of the company. You wouldn’t think it was the time or the place to start exploring solutions to world hunger, but that’s exactly what happened to one candidate looking to be a software developer at Amazon.

In Glassdoor‘s annual review of the top 25 oddball questions asked in job interviews in 2011, tech companies feature highly. Although there’s just one question from Google on the list, the Wall Street Journal recently profiled the search giant’s interview process, highlighting the trademark strangeness of some of the questions.

Google’s odd questions range from relatively straightforward mathematical brain teasers like, “Using only a four-minute hourglass and a seven-minute hourglass, measure exactly nine minutes–without the process taking longer than nine minutes,” to truly head-slapping queries such as, “A man pushed his car to a hotel and lost his fortune. What happened?”

Google isn’t alone in this practice. Apple, Microsoft, Facebook and many others have challenged the brains of prospective job candidates in some truly odd ways for a long time. Glassdoor has been publishing a compilation for only since 2009, but the idea has been around a lot longer than that.

The “oddball question,” of course, is meant to challenge the job candidate to think on his or her feet. It forces the interviewee to reach beyond prepared remarks and start engaging in problem solving on the spot. The best “weird” questions still have some relation to the kind of work the position entails. (For example, questions about finding the correct sequence could relate to jobs involving organizational systems.)

What’s the weirdest interview question you’ve ever gotten? Let us know in the comments, and browse the strangest interview questions from tech companies on Glassdoor’s list below.

“How many people are using Facebook in San Francisco at 2:30 p.m. on a Friday?” — Asked at Google, Vendor Relations Manager candidate

“If Germans were the tallest people in the world, how would you prove it?” — Asked at Hewlett-Packard, Product Marketing Manager candidate

“Given 20 ‘destructible’ light bulbs (which break at a certain height), and a building with 100 floors, how do you determine the height that the light bulbs break?” — Asked at Qualcomm, Engineering candidate

“How would you cure world hunger?” — Asked at Amazon.com, Software Developer candidate

“You’re in a row boat, which is in a large tank filled with water. You have an anchor on board, which you throw overboard (the chain is long enough so the anchor rests completely on the bottom of the tank). Does the water level in the tank rise or fall?” — Asked at Tesla Motors, Mechanical Engineer candidate

“Please spell ‘diverticulitis’.” — Asked at EMSI Engineering, Account Manager candidate

“You have a bouquet of flowers. All but two are roses, all but two are daisies, and all but two are tulips. How many flowers do you have?” — Asked at Epic Systems, Corporation Project Manager/Implementation Consultant candidate

“How do you feel about those jokers at Congress?” — Asked at Consolidated Electrical, Management Trainee candidate

“If you were a Microsoft Office program, which one would you be?” — Asked at Summit Racing Equipment, Ecommerce candidate

The Spark of Genius Series highlights a unique feature of startups and is made possible by Microsoft BizSpark. If you would like to have your startup considered for inclusion, please see the details here.

Each weekend, Mashable hand-picks startups we think are building interesting, unique or niche products.

This week we’ve chosen three new takes on established online staples: digital books, ID and shopping.

Booktrack, for instance, adds audio to digital books. Miicard provides reliable digital identity verification. And Grabio takes online classifieds local.

Booktrack: A Soundtrack for Books

Quick Pitch: Synchronized ambient sound effects for books.

Genius Idea: Technology that recognizes an individual’s reading speed and paces the soundtrack with corresponding text.

Mashable’s Take: Booktrack’s sound effects for iPad and iPhone books are designed to create a background soundscape that matches the text. Sherlock Holmes, for instance, opens with the sound of a heavy rain. At moments that match the text, there might be sounds of footsteps, an explosion or suspenseful music. A scrolling arrow keeps track of the reading speed at which the app is matching sounds to text and can be easily sped up or slowed down.

Says Booktrack founder Paul Cameron, “It makes a new and engaging way to read and really enhances the experience and enhances your imagination and keeps you in the story longer,” he recently told The New York Times.

PayPal co-founder Peter Thiel, the company’s lead investor, evidently agrees. HarperCollins, Penguin Books, Sony/ATV Publishing, and others have agreed to at least try the format.

Crazier concepts have succeeded, and other book platforms are experimenting with adding social networks and videos to texts — both of which are arguably even more distracting than sound.

But one thing I like about books is that they’re not movies. There’s an inherent silence on the written page that is part of the experience of reading and a pleasant departure from the constant pinging of screens.

It’s not hard to imagine that concentration on one medium at a time will become outdated. But for me, the written word is still perfectly adequate on its own.

MiiCard: A Digital Identity Card

Quick Pitch: A digital passport that proves ‘you are who you say you are’ purely online and in real time.

Genius Idea: Using verified online accounts to validate your identity.

Mashable’s Take: MiiCard is an identification “card” for the Internet.

Signing up for MiiCard involves the familiar process of verifying your email address. Before the site will vouch for your identity, however, you need to link to other accounts such as those from your bank, credit card and utility companies. Adding more links gives you a “stronger” identity verification.

After you establish your MiiCard identity, you can use it on its partner sites. When you attempt to purchase a product or service online, the “Level Of Assurance” that you need is pre-determined by the vendor or service provider and its regulator. This could be handy when buying and selling online or on an online dating profiles.

It might be hard, however, for people to hand over data about their financial accounts to a startup. The company tries to counter this hesitancy with a safety explanation: “miiCard uses bank-level security to protect your information — utilising multi-factor authentication and industry-standard encryption to ensure your data is secure.”

Grabio: A Location-Based Marketplace

Quick Pitch: A location-based marketplace that connects buyers and sellers within a predefined radius.

Genius Idea: An alternative to online listing sites like Craigslist that brings classifieds closer to their roots at local papers.

Mashable’s Take: Let’s say you want to buy tickets to a sports game at the last minute. You don’t have time to take an hour-long drive to receive them, and the tickets that people posted last month on sites like Craigslist have already been sold.

Grabio aims to be your solution. Its app lists items and services for sale near you in real-time and allows you to post things you’d like to buy (“Need two tickets to the Cubs game tonight”). Buyers and sellers can connect within the app to set up an exchange.

It’s an obviously good selling method for a number of items: tickets, textbooks on campus, dog walking services. But it’s so useful, Grabio has a slew of established competitors.

Zaarly focuses more on odd jobs and services (“Bring me an ice cream cone and I will pay you $10), Goshi hosts image-based listings and Taap.it also has a similar platform.

Grabio’s success depends largely on its ability to distinguish itself from the many other players in the space.

Image courtesy of iStockphoto, mbortolino

The Spark of Genius Series highlights a unique feature of startups and is made possible by Microsoft BizSpark, a startup program that gives you three-year access to the latest Microsoft development tools, as well as connecting you to a nationwide network of investors and incubators. There are no upfront costs, so if your business is privately owned, less than three years old, and generates less than U.S.$1 million in annual revenue, you can sign up today.

You may be purchasing services from people with magical talents (artists) and it’s a mistake to confuse them with vendors.

As we get more and more service oriented, it’s an easy mistake to make. You’re busy buying cleaning services or consulting or design, and sometimes the person you’re working with is a vendor, and sometimes they’re not–they’re an artist, “the talent.”

A vendor is someone who exists to sell you something. It doesn’t always matter to the vendor what’s being sold, as long as it’s being sold and paid for.

The quality of what’s being delivered is rarely impacted by the method of transaction. The turnips will still show up, the house will still get painted. You can send an RFP to a vendor, bid it out, get the lowest price, sign the contract and if you write the contract properly, will get what you ordered.

The quality of the work you get from the talent changes based on how you work with her.

That’s the key economic argument for the distinction: if you treat an artist like a vendor, you’ll often get mediocre results in return. On the other hand, if you treat a vendor like an artist, you’ll waste time and money.

Vendors happily sit in the anonymous cubes at Walmart’s headquarters, waiting for the buyer to show up and dicker with them. They willingly fill out the paperwork and spend hours discussing terms and conditions. The vendor is agnostic about what’s being sold, and is focused on volume, or at least consistency.

While the talent is also getting paid (to be in your movie, to do consulting, to coach you), she is not a vendor. She’s not playing by the same rules and is not motivated in the same way.

A key element of the distinction is that in addition to the varying output potential, vendors are easier to replace than talent is.

Target understood this when they reached out to Michael Graves to design a line of goods that sold hundreds of millions of dollars worth of items. When I interviewed Michael a few years ago, he had nothing but great things to say about the way Target invited him in and gave him the ability to do his work. Threadless embraces this when they treat the designers of their t-shirts in a non-corporate way. Etsy is built on this single truth.

Most industry is built on vendor relationships, and vendors expect (and sometimes value) the impersonal nature of their relationships. This scales… until you lump in the talent.

Should you treat vendors with respect? No doubt about it. Human beings do their best work when they’re treated fairly and with enthusiasm. But when the provider is also digging deep to put something on the table that you can’t possibly write a spec for, you’re going to have to respond in kind.