Not in the same group. Not necessarily overlapping groups.
My feeling is that these folks put out a lot of disinformation to make it hard to tell when real messages are sent out.
Also, some are simply people who hate America and get together online to chat and spout their feelings.
Put all these sites together and it's easy to understand why the authorities have such a hard time distinguishing the "real" from the "hooey", which makes it hard to issue warnings.
That's my take on it, any-hoo, based on the things I've seen here.