Re: No fan of Sony, but...
So pick a side: is digital vigilantism illegal, or not? If it is, then it is as illegal for a corporation as it is for an individual, full stop.
Trevor is right. Pick one and then live with it. If you say it's ok because Sony is an asshat, then what will you say when someone tries to pull the same crap on you or your company? The laws and rules in most places is blind in that it applies to everyone and every company whether they're asshats or not.
Maybe they're doing the right thing in poisoning the torrents in their collective mind. But the table is turned and they get the same medicine, they'll howl up a storm and cry and sue. They can't have it both ways.