Ones I will never give money to anymore:
Ozzy Osbourne - Paying for anything involving him is like giving money to that evil witch he calls his wife and that ain't happening. Ever.
Eddie Van Halen - What happened to this guy? Did the Hagar and Roth fiascos in the mid 90s really turned him into this big of an a-hole, or did he just really hide it well for a long time?
Axl Rose - THE biggest d-bag in rock, bar none, but seeing that I am not much of a fan of GnR, outside of a handful of songs, I would never spend money on their albums or concerts anyway. The only times I have owned any of their albums were used copies I got for really cheap at a used CD store, and the band never sees that money.
Ones I sometimes have to think twice about:
Roger Waters - I'll usually pony up if it is something I really want, but I won't go overboard. For example, I would have liked to have seen The Wall show he did here in late 2010, but I refused to pay nearly $200 for it.
Mike Portnoy - He is involved in too many projects I already love (Neal Morse, Transatlantic, etc.) to write him off completely, but I am a lot less likely to check out and spend money on any new projects of his than I was two years ago.
I think that's about it for now.