Neopets was where I first discovered hacking.

There was a user named "blueyoshi82" or something, I wanted to see if I could get into their account (I don't remember why). So I tried guessing their password, and lo and behold, it was just "yoshi"!

Being the white-hat that I was, I tried to PM them a message saying "hey you really need to change your password, it's too easy to guess", but the word "password" was blacklisted so I couldn't tell them.