Like everything else Facebook does, today's introduction of Interest Lists is about keeping you on the site longer.
While some are comparing the lists to the similar feature Twitter launched in 2009, remember that a Twitter list simply organizes people you follow and still has you clicking links to source sites. Facebook lists, on the other hand, organize content from your news feed and makes it more manageable. Like Social Reader, the idea behind Facebook Lists is to give you third-party content within Facebook.
The lists also add to the reams of data Facebook already has about your likes and dislikes, helping the company better target ads. As AllThingsD points out, that gives Facebook a work-around recent Pew Research data showing that more people are unfriending on social networks, meaning theoretically we're getting exposed to less information every time we log into Facebook.
The trade off for you is that more relevant information shows up in your news feed. In addition to pre-populated lists like NFL Teams and 2012 Presidential Candidates, Facebook gives users to make lists on topics of their choice. Greg Finn of Marketing Land says the process is incredibly simple: he populated a list about search engines in less than five minutes.
The feature is being rolled out to all 645 million users in the coming weeks. You'll get list recommendations based on your friends and interests. Whether or not the ploy to increase advertising is largely left in users hands: if they adopt the new feature, advertisers will certainly follow. But if the lists don't bring real value to users and end up being just another thing for them check, Facebook could be back to looking for another way to target advertising.