All of them are legit... the fan pages are run by fans (improved by the guys) and the personal page of Mark's is run by Michael most of the time.
Here's some tweets from Jef Moll (AB's Engineer)...
"Alter Bridge is working up a song that seriously is giving me the chills!"
"Alter Bridge prepro... No place I'd rather be"
http://twitpic.com/1120gu
You can follow him at the link below...
http://twitter.com/1f_jef