Anyone having success charging for something on Facebook?

Also are there any numbers on how much money Facebook makes off the 'gifts' they sell?

I'm trying to decide right now between the prospect of charging a minimal fee for something and necessarily limiting my audience vs offering the service for free and attempting to make money off a large(r) audience with ads. I guess it is a question that most startups end up asking.

Does it seem like Facebook users are willing to spend money?