I have left a band because I couldn`t put up with the singers attitude and I was one of the founders of the band and the driving force at first. And I have left another due to the crap music (IMO) we were playing. And the drummer was crap as well and they ended up getting shot of him.
But I am on friendly terms with all my ex bandmates, which is just as well as you will more than likely meet up with them at studios or gigs. At the end of the day, if you are doing music for fun and it stops being fun, you have to go with your insticts.