There are photo sites where you can rate people's appearance on a scale of 1-10. The average average should tend to 5.5 with enough data (or 5.0 if a scale of 0-10 is used).

However, it is rare that any photo, regardless of appearance, gets rated less than 5.

Revenge is unlikely since voting is anonymous, and there is no requirement for voters to post their own photos.

EBay's rating system is intended to have an economic, rather than aesthetic basis. However rating inflation is common to both systems. Altruism? Guilt at giving bad ratings?