I had a friend complain that someone was bugging her to help them with their "farm" on FB. I didn't know what the heck she was talking about 'til I read an article about some guy making a killing on this scam, excuse me game. I think the operative factor there is that the games are tied in with the whole addictive nature of social networking and interaction. I'd be looking at how to capitalize on that. If you can make the products somehow part of the interaction, then it could take off. Given FB's notoriously cavalier attitude toward privacy, I definitely couldn't see shopping there but I'm sure there will be no shortage of folks who will do so eagerly. 

"Democracy is a pathetic belief in the collective wisdom of individual ignorance." - H. L. Mencken