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Snooping on user profiles isn't the only special privilege Facebook employees have. They also get to test the site's latest features. Like news feed voting. Above is a mockup of my news feed as a Facebooker would see it, based on real screenshots from an inside source. (Showing a screenshot of his actual news feed would out my source to Facebook management, I fear.) Notice the "plus" and "minus" buttons? Those are new. Not yet available to the public, those will allow users of the social network to vote on items that appear in their news feeds. The news feed is a stream of friends' activities on the site, filtered by Facebook's algorithms which try to predict what you'll find interesting. Voting means users will have active input into those algorithms. If you're thinking "cute feature," think again. Here's why Facebook's voting-rights move is worth watching.

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The first reason? Data is king, and the promise of detailed data about its users provides most of the justification for Facebook's lofty $15 billion valuation. If most users are like me, I figure they skim their news feed, not clicking on most of the items. Facebook doesn't get feedback on items they like but don't click on. Voting will actively feed users' preferences into Facebook's algorithms, making them smarter — much as Google's search algorithms constantly improve by tracking queries. In the example above, I'm informing Facebook that I like to hear about new Valleywag fans — but Facebook fanboy Dave McClure's latest app installation? Sorry, Dave, I can't do that.

Data-gathering is key. But the second reason is the growing controversy over Facebook's plan to place ads in users' news feeds. Those ads will be generated by friends' activities on advertisers' sites and on Facebook product pages. Some people are already complaining that Facebook doesn't make it easy for users to avoid these ads.

It's not clear if the voting mechanism will be extended to news-feed ads, too. But it would be a smart move. Don't like an ad? Just click the "minus" button, and similar ads will be less likely to show up in your news feed the next time you log in. Facebook's ad systems, too, will learn which ads are most effective for which people. Advertisers might squawk at first that users can nix their ads, but since the whole point of Facebook's new social ad system is to target ads to users inclined to be receptive, they're likely to grudgingly go along.

The third way this could matter? The voting mechanism, right now, appears designed to tweak individual users' news feeds. But there's no reason Facebook couldn't use it to gather insights across its 50 million users, and show, say, the most popular news headlines across the site. Voting on headlines: Isn't that Digg's business? And wouldn't Facebook's entry into the social-news marketplace roil any plans Digg might have to sell for a price of $300 million or more?

There's no word on when Facebook users will actually earn the franchise. But since the voting feature's already rolled out among Facebook employees, it seems close to market. Will it click with users? Soon enough, Facebook will be counting the ballots.