The whole world uses Facebook, yet the social network still hasn't found a way to properly monetize on that potential (or just hasn't revealed these plans yet). Sure, they've got the ads but while Darren Barefoot was successfully guided to a cool band they were trying to sell me a fake Rolex the other day.
Facebook is probably not so desperate that they are going to try and earn their lunch money advertising fake watches from China, but this still left a bit of a bad aftertasete. Globally, counterfeit watches are estimated to cost the Swiss watch industry alone more than $600 million per year. I doubt Facebook wants to be known as a platform for this massive black market – it's certainly not reputation enhancing.