I actually looked into this yesterday. Since the opening of the voting, 51 new accounts were created from 44 unique IPs. Some duplication is to be expected from people in offices, family members sharing a router, etc. There were no clear or suspicious patterns to usernames / email addresses. While I can't rule out some sockpuppetry, if it happened it wasn't on a particularly large scale. If they did send out a message on Facebook asking their fans to sign up and vote, that's certainly allowed, so long as there was only one vote per person.
If there is a perception that there was sockpuppetry, it may stem from these 4 posts, made by accounts that just signed up:
AVS
Norris
Burnz N' Hell
Posted on: January 04, 2010, 02:34:15 PM
AVS
Norris
Burnz N' HellSomeone plz tell me who the drummer of AVS is. I'm a SWM looking for some fun. Peace.

avs can s my d anytime
Bringing out your fans to a Battle Of The Bands is a valid way of getting a win, just as it was here. They've lasted longer and done more touring than at least 90% of the nominees, so I have no doubt as to their validity.