I think it's sad that negative feedback might even be merited, first of all. That being said, I'd much rather that negative feedback be left than have traders blacklisted through 'naughty trader lists.' With all of the PM'ing of 'naughty traders' names going back and forth, it made me feel like I was back in 4th grade again. This is what the feedback system is for, after all, and it should be used appropriately.
That being said, I just hope that ALL feedback that is given (positive, neutral, and negative) is given because it truly is DESERVED, not for other reasons. I would hate for someone to give positive feedback when negative is deserved because he/she is afraid that the other party will retalliate and give negative feedback just because he/she deservedly got negative feedback instead of giving the positive feedback he/she should have given. At the same time, I would hate for someone to abuse the system and give negative feedback for no reason at all, just because he/she can.