360-degree appraisals can be biased in many ways. For example, if I see my colleague doing really well (and I am jealous), so as soon as I get an opportunity to give feedback, I might try to pull him down. You know, I might purposely give wrong feedback just to pull him down. Apart from that, to improve overall scores, colleagues may join hands to rate each other highly and stuff like that. Otherwise, it usually happens that if, for example, I don't like X, then chances are that I will not talk or write well about him. You know how personal issues can affect our job.