The hack on HBGary federal was one of two things.
1) Revenge, maybe they DID know who it was running the group and they were attacking the servers out of self preservation and just stumbled across the information that was released.
2) Protection of innocent people, they attacked HBGary Federal to stop the release or convince them to stop the release of incorrect names, and just stumbled across the information that was released.
I think a combination of the two is more of what really is going on, from all of the stories I have linked here and read it appears that he did have a few of the names right, and I have even seen the mention of a family member or girlfriend being named along with some people that are way off the mark.
So what really was the motivation of the attack? While the information that was released was great, it was an accident, if there was a good password policy going on this may not have happened and the site just would have been defaced. Or was it the intent from the begging to take them down and rootkit.com was just low hanging fruit along with all of the emails?
It does get the mind working.