Just a little anecdote that I've found interesting since I started my music website HypedSound. I'm completely redesigning and relaunching the site with the same community and a new vision in a couple months, but right now I still have a paid featured artist spot on the homepage. I've had a fair number of people pay for this spot and not one single person has complained. Nothing about wanting their money back, not liking that they paid for it, or anything. Sometimes I feel like the people who pay for an app or feature of your product are less likely to complain than someone who uses it for free. That being said, at the moment I think they have every right to complain because the site is slow and clunky and lacks any sort of design hierarchy or central theme :)