The current Atomic Robo storyline (http://www.atomic-robo.com/atomicrobo/the-dark-age-page-1) is a pretty good summery of why I've written off mainstream comics.

Comic series are constantly being rebooted / relauched / reconned. Combined with the mini-series and spin-offs, it is difficult to follow. Additionally, "shocking" revelations and plot-twists only survive until a new writer is assigned the character.