The majority of the high-scoring successful players have been playing since before the Open Beta. None of them are playing multiple IDs.
You know this is a BUG in the chat, right? That when people type it comes up saying it's the wrong person? One of the people in my team keeps getting labelled as Africa by the team chat; this doesn't mean she's playing in Africa and our civ.
No, I didn't know that. I think this is at least an equally plausible explanation in the case of the people I thought were doing it. I'm going to drop this inquiry for now, till I know more.