You can also create your own social network for the same reasons plus you will also increase your own profile. With Ning, it couldn't be easier. First, though, I would recommend that you research what networks already exist similar to what you have in mind.
Is there already saturation? This would mean that it will be very difficult for people to be attracted to your network.
Or do you feel that there is room for your network? Go ahead - it doesn't cost anything. Once it starts to take off, as I said, it will help elevate your profile on the web and bring more traffic to your blog(s) as well as giving you the opportunity to network with similar people or people with similar blog(s).
I myself have just started a network for bloggers over 50. I've called it O Fab!! - Over Fifty And Blogging. Fab is very much a word of the sixties, so the initials suit. It's just going to be a relaxed place and I'm just going to see what interest there is and how it goes. I feel that bloggers over 50 - whether they are doing it for money or just as a hobby - have a certain 'maturity' to offer to the world of blogging!
So, if you are over 50 and blogging, do come and join here. I'm neither technical nor artistic, so I'm not particularly happy with the logo at the moment, but when, hopefully, the membership increases I'm going to see if someone would like to design something better (and get full credit for it on the main page, of course).
Visit O FAB!!