Chas,
That makes sense that social networking sites may be part of the reason for a decrease in activity on photography forums. I have a facebook account, but I don't post on it often and I rarely use it to post photos. I have not used flickr or any of the other sites, although I've browsed them a couple times. I find the volume overwhelming. One of the things I like about a site like ours is the sense of community. And it's a community small enough (OK, too small right now, but in the past...) small enough to know each other. I guess the giant photo sharing websites have so many sub-forums I could find one of those and it would become a new community to me. I could be wrong, but I'm under the impression that those sites are more for photo sharing and less for tutorials, teaching each other, and extended discussions.
Courtney