Why is Facebook so hellbent on being an advertising and marketing company? Nobody wants to see ads when they're reading up on their friends' lives, and people will leave in droves if they feel like their private info is being overly exploited, or if they're constantly bothered to participate in stupid marketing surveys.
People spend money in social contexts, why not try to take a cut? Let event planners set a price for events, and take a small cut. A group of friends wants to go to a movie or a concert? Make it trivially easy to set up the time and place and take a cut of the ticket sales. Someone's birthday coming up? Let groups of their friends make a group purchase from their Amazon wish list and take the sales commission (then gradually phase out Amazon). Where's Facebook's version of Paypal, OpenTable, etc?