So far as I have observed, while the group is loosely-knit, and really is in concept "anyone" -- in terms of general perception by media and people there rather actually is some consensus of who is more Anonymous than the other.
And that's on the basis of who historically carried out most of the attacks, as were reported/confirmed on Twitter by Sabu ( https://twitter.com/anonymouSabu ) and AnonymousIRC ( https://twitter.com/AnonymousIRC ). Sabu was the de facto leader of LulzSec (the most technically able person in LulzSec -- the only member of LulzSec who's in fact still on the run) and he seems to be promoting the leak pretty persistently. AnonymousIRC did also take responsibility for this one.
And that's on the basis of who historically carried out most of the attacks, as were reported/confirmed on Twitter by Sabu ( https://twitter.com/anonymouSabu ) and AnonymousIRC ( https://twitter.com/AnonymousIRC ). Sabu was the de facto leader of LulzSec (the most technically able person in LulzSec -- the only member of LulzSec who's in fact still on the run) and he seems to be promoting the leak pretty persistently. AnonymousIRC did also take responsibility for this one.