The uniqueness validator was always case sensitive but that seems wrong because we want uniqueness validations to be insensitive in most of the time.
Do not make more sense be insensitive by default and set sensitive only where it should be?
We are migrating a lot of big applications from mysql to postgresql here and we are setting case sensitive to false on **all** uniqueness validations.
Note: mysql do not differ case by default, so, it work as insensitive in all situations.
Rails will change the major version on 4.0 release and could be a great time to do that if core team agree