Lol people flip out about -rep it is quite funny even if it gets reversed. Funny because -rep is only -1 point where as +rep can give u +10 off some people so its really not a issue lol.
Generally I stay away from giving negative rep, and yeah - I don't really see people use it often. Even if I disagree with someone I don't usually find myself in a situation where it's necessary. I guess it's circumstantial. I feel like the offenses that might really bother me would probably be moderated by a mod anyway, heheh.