The stars can't have anything to do with the post count, because I had 30k posts back when there was no fifth star...
My deductive skills are impressive.
Do you also remember how you got the 4 stars before that or is that part of your memory destroyed by alcohol and/or overwritten by images of Kate Beckinsale?
There clearly needs to be one greater internet points system so no matter where you get the points, they're visible everywhere. You'll be able to swing around your e-peen anywhere!