After four years of quietly trying to take on Wikipedia, Google (Nasdaq: GOOG) is shutting down Knol. The world's leading search engine is advising contributors to the fledgling destination that it will shut the site down in May.

"Google's chances look good," I argued shortly after its launch. "Wikipedia's anonymity and ad-free design are virtuous, but some writers need better incentives."

See, unlike the top living and perpetually tweaked encyclopedia, Google was giving authors the ability to both claim their contributions and to make a little money by allowing Big G to place ads on their pages. It should have worked. Google's AdSense monetization program has helped the success of countless third-party websites as well as the dot-com giant's own Blogger and YouTube publishing platforms.

Unfortunately, Google never gave Knol a real chance to succeed.

For starters, there was already a Knol.com when Google launched its site. It's the name of a Dutch company that's been providing cleaning solutions since 1969. Google stuck with Knol -- a unit of knowledge -- and simply tucked the destination away as a subsite at knol.google.com. It's safe to say that Wikipedia would not be a hit today if it was simply a subdomain with a difficult Web address.

Google also never really promoted the site. It's not as if Knol results ranked higher than Wikipedia entries on Google's own site. Outside of early contributors, most Internet users probably didn't even know that Knol existed.

Providing financial incentives seems like a no-brainer, but dot-com giants haven't had a very good track record here.

Amazon.com's (Nasdaq: AMZN) A9 search engine offered shopping discounts to users -- until it didn't. Its Askville Q&A site was originally designed to give contributors points that could be redeemed for prizes on a Questville site that was supposed to eventually launch -- until it didn't. Microsoft (Nasdaq: MSFT) tied financial incentives to its comparison-shopping site -- until it didn't.

Successful monetizing efforts have come from unlikely players including the Liberty Media-backed Lockerz and United Online's (Nasdaq: UNTD) MyPoints.

Knol will become one of the many online initiatives that Google has nixed too soon, largely as the result of coming up short on the promotional end. We'll never know if the Knol model would have worked under kinder conditions, but I guess that's the way the Knol tolls.

If you want to follow Big G developments as they happen, add Google to My Watchlist.

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Longtime Fool contributor Rick Munarriz calls them as he sees them. He does not own shares in any of the stocks in this story. Rick is also part of the Rule Breakers newsletter research team, seeking out tomorrow's ultimate growth stocks a day early.