I think I've only had 3 out of 120 not fund (and one of them was non-rpg related, where they emailed me and offered the reward anyway if I sent them the money, which I did).
It's the ones that fund and then don't deliver that are depressing. I went through a very bad phase where of the first 15 kickstarters I backed, three of the creators delivered next to nothing (although one of them was saved by a third party stepping in).
Since then I've had another five fail to deliver, for various reasons.
Also three more where some stretch goals have been outstanding for a very long time (but which I'm not worried about, since I've already had my money's worth).