Poiuyt had his key revoked because he took TomTheGeek's key and forum account because TomTheGeek was stupid enough to sign up for Poiuyt's forums under the same password he uses for his email. His brother (my former best friend) also had his key revoked because he uses the same IP as Poiuyt. They have played since then, though.
Plaz had his key revoked for overusing a script that fake grabbed everyone at the server's keys. It would generate a bunch of gibberish with the right amount of characters and make everyone flip out, and then he'd leave. He did it many times and got his key revoked.