How Facebook Knows What You Really Like: http://www.wired.com/wiredenterprise/2012/05/facebook-open-graph/
Forget the title of this article for a second. Read this and imagine how FB has set themselves on the road to becoming such a vast monopoly on information that even Microsoft would be flabbergasted at their ambition. I'm not sure competition regulators would be aware what is going on because this isn't traditional competition. ("We don't own the information, we're just organising it.")
Besides, this is all moving really quickly. European competition regulators, who are perhaps the world's most prolific, have only recently turned their attention to Google. I can't imagine they'll think about Facebook in a hurry.