Overnight, Communities appeared on Google+. Like you, my first thought was Oh no, closely followed by Do I need another online space?
Most people feel that Google+ is already too confusing, but in fact, Communities do look to offer a valuable new space. Unlike Google+ Pages, which are primarily a broadcast tool, Communities are much more open and designed for discussion. They are also more suited to professional use than other aspects of Google+ and provide a valuable differentiation of this service from Facebook, which most people want to use for friends and family.
So is this the long-awaited replacement for friendfeed? I suspect not. Although it probably has the right attributes, it's too late now to win the uphill struggle against Twitter. At the time, friendfeed didn't have any real competition in terms of professional online discussion space. I think it's probably now too late to woo people away from the deficient charms of 140 characters. I hope I'm wrong.
However, Google+ Communities may have their uses. They might well be more suited to courses and modules than a simple Google+ public stream. (Sadly, posting to a Google+ Community also spams your Google+ public stream.) However, until they prove their worth, I'm sticking with dark social because it's working for me.
Update: I see the Higher Education Community tag has already been grabbed by "Marketing and Communications Professionals". Hmm, land grab? I wonder how Google will resolve name disputes?