Ahh.. ricers, great expression, and works just as fine on computers. I don't really hate any mods though, but i would never keep a case that someone butchered and made into a 70's discoteque..
Ok, so some stuff that i think should be outlawed in computer cases..
- Neon lights, ccfl's and blinking stuff
(unless you actually use it for something, i have a white ccfl on a bendable thingie.. don't know the word.. as an extra lamp primarily for when i have to do stuff inside the computer)
- large windows
(unless you actually cleaned up inside the case so it's really nice to look at, i've maybe seen ten cases ever with the insides looking good enough to show off)
- forgetting to paint the cd/dvd's
(this is just not acceptable.. if you put a lot of work in painting your case, you just can't forget the drives)
- biohazard/radioactivity fanguards
(nope, can't think of any exceptions here..

)