After reading the /LFG thread, it brought to mind the idea of rating players after a group experience.
After you leave a group, group members are prompted to rate you.
After someone leaves a group, you a prompted to rate them.
Could be as easy as a simple window pop-up with a 1-5 star rating of different characteristics of your class.
Yes, no?
Players and guilds gain a reputation without needing something like a built-in rating system. This seems too easy for those "bad/evil" players to use as a weapon against other players. If you group with someone early in your grouping career and they decide to rate you an undeserved 1-star after the group then your own rating looks pretty bad and may make it difficult to get another group. Not a good early experience. Other unfortunate situations may also cause similar downvotes even if they weren't really your fault.
It *might* work if your rating wasn't shown to anyone until you have some minimum number of votes so you can mitigate the effect of the above situations. But these ratings might also discourage grouping to begin with, or at least discourage grouping with people you don't yet know. That seems antisocial to me.