Yes, but...
If one is looking for numbers, then no doubt Facebook is the place to be.
But then you get all of the wankers, malcontents, and dumbos.
No, thanks. I'd rather deal with mature, intelligent people who are passionate about photography than the bitchers, moaners and know-it-alls that inhabit unmoderated sites.
Michael
I agree. "Social media" are a modern day IRC - a huge waste of time and socializing for the sake of socializing. It's a digital equivalent of sitting in a pub all day and not having a life. Topical forums built around real content, such as this one, can also be called social media, but the quality of information exchanged is much greater.
I don't oppose facebook or g+ as personal registration services that could replace multiple login accounts for all kinds of discussion boards (such as this one) in the future, but as things are now, trying anything there is like going to the main city square because that's where people are, and try to make a conversation about any specific subject. Signal to noise ratio is *so* going to suck.