I had my freakin' debit card numbers used fraudulently, on some World of Warcraft gaming accounts and an expansion package (I have no clue). I also had them used on skype.com, so I'm currently out $93 total till the bank can figure it out and pay me back. And right now, that's a lot of money for my poor self. (I cancelled the debit card right away too, so it can be used anymore)
Sooooo, lesson is to frequently check your statements online!