The thing about Anonymous is that it's a lot like Bitcoin; it's decentralised. There are no leaders and there's no "initiation" to become a member, so to speak. Anyone can claim to be a member and anyone can declare war in Anonymous' name. The success of each of their little vendettas depends on how many other "Anons" want to help them.
Yeah I guess you're right. Maybe the message
"We are anonymous. We are legion. We do not forget. We do not forgive. Expect us."
could be translated into:
"People exist. They are numerous. They don't forget. They don't forgive. Fear them."