Facebook is testing a new way to rate Places that is reminiscent of another successful Zuckerberg project, Facemash. Some users who have checked into Places, or who have been tagged in checkins, are seeing a new sidebar asking “Which place do you like better?” When a user chooses a place, the section pits two more places against each other, and so on.

(Facemash did this with photos of Harvard students and asked people to choose the more attractive of the two.  If you’ve seen The Social Network, you know how instantly popular it was.)

When Facebook launched Places in August 2010, it was clear that the product could one day have options to rate and review places a la Yelp. Since the site has such a massive user base, there is a great opportunity for Facebook to own the social recommendation space by making a product that becomes even more widely adopted. As it is now, lots of people who read Yelp reviews have never written one themselves, nor have their friends. A lot of companies are making social sites and apps to share information and recommendations, but none have been able to solve the problem of participation inequality. I believe Facebook is more likely than anyone to figure this out.

This latest test shows just how clearly Facebook understands human behavior. If they had asked me to rate Free State Brewing Company, I might have done it only because I like that place a whole lot and want people to know about it. If they asked for a review, I might not have because I like that place a whole lot and would want to take some time to write a great review. Instead, Facebook made the question so simple and compelling that I continued to vote until I didn’t have any more checkins to vote upon.

This may not be the ultimate way Facebook implements recommendations, but it at least shows that they get it.