I once decided that an RP I had a hand in creating could go hang, but it wasn't so much that I hated the idea and more that I hated how the group had turned out. That being how the characters in the RP acted, or how they were managed by their players. I just couldn't stand to be a part of it anymore, so I just let it fall when it started go inactive.

I also called it quits on an RP I started once, but again, it wasn't that I hated the RP, but felt that I couldn't really accomplish what I had set out to do. I had wanted to have a sort of faction dynamic going on, but eventually there was too few people to have meaningful divisions.