According to Sam Lingle at Amped eSports, Blizzard has disqualified several top teams and many players from its Arena tournament regional in San Diego. The top eight arena teams lost twelve players, leaving three of them unable to compete at all and two more missing key players. While previous rounds of disqualifications were due to location issues (sorry, Canadians), these DQs were for players whose names didn't match up with the names paying for their accounts. While theoretically, this could be caused by someone using someone else's credit card (like a family member's) to pay for the account, it's more likely due to account sharing -- which many of the players admit. Of the four disqualified players Lingle interviews, three say it was due to account sharing or just plain buying/taking over accounts. Note that Lingle's story is pretty dang biased in favor of the players, so I would take the whole interview with a grain of salt.
On the other hand, I'm also not trying to compete nationally in WoW, and the excuses used by the players just suck. Leveling is a "huge time commitment"? No, you've had like two years to level. Endgame raiding is a huge time commitment. Leveling can be done practically in your sleep. "Because 1-60 is terrible and when u need a class u can't really wait for someone to level and gear so they get characters from a friend or whatever"? If you're seriously competing at a professional video gaming level, is it too much to ask that you put the relatively minor amount of time into leveling your own character?
There's a big discussion about this on the forums, and I can see both sides. What do you think?