Every good thing has a limit. When you pass that limit, you've overdone it and the good think becomes an annoying thing. Here are two examples (in my humble opinion):
Everyone loves Rhianna and I'm no different. However, I do think shes taken the whole "I'm a fashion-forward, edgy, warrior princess" look a bit too far. Theres a difference between being fierce and becoming a gimmick. I think Rhianna's style has crossed over into the gimmick arena.
The Twilight Cast - Kristen Stewart and Rob P:
Okay, we get it...you guys are reluctant celebrities. Acting is your craft and you can't figure out what the big deal is. But seriously, that doesn't mean you have to ALWAYS look like you just woke up, crawled out of bed, and hopped onto the red carpet. A little effort and grace on your part would do everyone some good.