Just one observation...
Facebook Pages is really just a blogging platform if you look at it. And Facebook Groups is really just a discussion forum platform.
The only difference is that Facebook doesn't allow its users to monetize the traffic they attract to their Pages and Groups. But if Facebook were to change that, setting up a revenue share?
Facebook already has its own AdWords system in place in form of Facebook ads. They can certainly create their own AdSense system too. And if they implement their own AdSense system on Facebook Pages and Groups, it rushes in a flood of "Facebook publishers". As it is now, Facebook users already know how to create their Pages and Groups, compared the smaller number of people who know how to create blogs and forums.
So instead of thinking about Facebook beating Google in traffic referrals, think about Facebook creating their own mini-Internet, and reducing the need for anyone to leave Facebook.