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.
For those who don't know who "Sabu" is:
Sabu is an alleged leader of the hacking group LulzSec. He features prominently in the group's published IRC chats, and is a supporter of the "Free Topiary" campaign.
The Economist refers to Sabu as one of LulzSec's six core members and their "most expert" hacker.
Unfortunately for Anonymous, false-flag ops against it are entirely too easy to pull off. Perhaps if it had some way of identifying itself with a public key...
Yep, saw that coming. Some people tried to build a group identity and reputation around the name "Anonymous", made it fashionable, and now every spook, wannabe-spook, and random vandal uses the name, regardless of whether they're associated with the original group or not.
As I said, it's tough to be anonymous and not be spoofed at the same time. Perhaps this is not the real anonymous? Or maybe it is. This group is vulnerable to having their aims completely diluted for precisely this reason - that they are anonymous :P
The question is - does anyone at Anonymous actually know if the other people were not also part of Anonymous? Why do they have any more right to be called Anonymous than someone else? Oh the anonymousness...