(also goodreads, etc.)
I want to have a strict voting scale, where most books get 3 out of 5 maximum stars. The problem is that most sites naively average all votes, and that if abook averages 4.2 or 4.3, people say it's "good".
The effect of me trying to keep a reasonable average rating is that my votes lower the score of the whole field of books I am interested in. This is not good.
Say an item's rating is now 4.5, and I think it should be 4. I could vote 4, but at this rate we'd never get there. If there are enough ratings on it already, I should just vote 1 to lower the rating & maximize my power.
So, this type of rating system rewards people who try to maximize their power, and punishes people who are straightforward & vote what they believe.
First, they should at least weigh the scores per-user. So that getting a 4 from someone who averages 3 would be better than getting a 4 from someone who averages 4.999. This is exploitable, so cap it.