Community management by defintion includes "PR" in that it includes "Public Relations", but a good community manager is much more.

They're often there to help facilitate conversations, user group meetings, keep the community civil, agitate for better customer support, and so on. Yes, they're cheerleaders to a certain degree, but pretty much any customer/public-facing role at a company needs to have a bit of cheerleader in them.

A whinge about nomenclature is what I got out of it. At SimplyBuilt we have staff members that foster communication, provide support, and delete spam/irrelevant posts. In our case (and in most cases I guess) the word 'community manager' would have a high handed sound to it, even though they are technically managing a forum.