Then could let everyone start with 100 one star ratings. If they rate their first thing it counts as 1/101 vote. If they start with a one star rating it will be their highest ever.

Alternatively you could apply the same rating to the customer and display it next to their user name along with their own review counter.

What also seems a great option is to simply add up all the stars :) Then the grumpy people wont have to do anything.