Facebook isn't going to create the world's largest marketing database? Could have fooled me. This week, the site added a "Like" button that allows users to rate content -- you either like it, or you don't.

You can guess the implications. The more you rate content, the more Facebook knows about you. And the more it knows about you, the better it gets at knowing what polls to invite you to participate in, and what ads to show you.

As a daily user of the site, I don't mind. But FriendFeed might. If you haven't yet been introduced to FriendFeed, it's an aggregator for the truly caffeinated among us. Twitter, Delicious, LinkedIn, blog feeds -- you can track all of it in FriendFeed. But without excellent tools for organizing data, FF is the Web's version of white noise.

For FriendFeed, "Like" is an organizing tool. It's a way to separate digital wheat from chaff. Facebook has a different idea. As product manager Leah Pearlman explained in a blog post:

This is similar to how you might rate a restaurant on a reviews site. If you go to the restaurant and have a great time, you may want to rate it 5 stars. But if you had a particularly delicious dish there, and you want to rave about it, you can write a review detailing what you liked about the restaurant. We think of the new "Like" feature to be the stars, and the comments to be the review.

Facebook's "Like," in other words, is a data point -- a way to know more about you. To Facebook, that's got to be downright mouthwatering.

Facebook said as much in refuting rumors that it had introduced a new polling product during the recent World Economic Forum in Switzerland. "The polls run at the World Economic Forum were not part of a commercially available product for advertisers and should not be confused with Facebook's Engagement Ads," the company said in a statement. Continuing:

Facebook has, for many years, allowed the targeting of advertising in a non-personally identifiable way, based on profile attributes. [Emphasis added.]

Of course, this is what everyone who makes a living from Web advertising does. Google (NASDAQ:GOOG), Yahoo! (NASDAQ:YHOO), and News Corp.'s (NYSE:NWS) MySpace all live off data. Microsoft (NASDAQ:MSFT) knew exactly what it was buying when it invested $240 million in Facebook.

I suspect that Mr. Softy is happier about that deal today, now that its good friend Facebook is getting to know you better.

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Fool contributor Tim Beyers had stock and options positions in Google at the time of publication. Check out Tim's portfolio holdings and Foolish writings, or connect with him on Twitter as @milehighfool. The Motley Fool is also on Twitter as @TheMotleyFool. Its disclosure policy is suitably caffeinated, thank you.