I am surprised that nobody has mentioned the Netflix rating system which seems more accurate. Netflix scales the rating against your other ratings. If you always say 3 = OK then 5 = great. If you always say 5 = does not suck then 3 = sucks but not horrible.

I don't even rate AirBNB hosts (for instance) because I know that a good enough host will be punished. I only rate the top and the bottom because those are the only two ratings that have meaning any more.