What ever happened to just talking to people in coffee shops. Opps I forgot you live in the big city. They would look at you as if you had dropped in from Mars or Salt Spring.

If by "social networking site" I can qualify my car club's website, then yes.  I am also a part of Active Rain, but honestly don't understand what it does for me, except give me a place to link and hopefully up my website's searchability!  

My car club however - www.fastgm.com - has gotten me prospects and the highest percentage of closings of all my marketing efforts!!  These are mostly friends and friends of friends, but the site is open globally and we market the heck out of it, so I get people from all over.  My latest is from Michigan (i'm in SC!)

My "signature" at the bottom of every post has the link to my website and there is a "vendor" section of the forum where I post regulraly - new mortgage packages, market news, recent club-people closings with pics, and thank yous ("next round is on me") for referrals.  

I think if you can find something popular to join that has a website that let's you post your link and "peddle your wares," AND you truly love the content or reason for the social site, you will do some decent business from it.  Best thing - it's the only thing I've done that is 100% FREE marketing.  

PS, I just joined myspace (late bloomer) specifically for biz, and I really don't like it so far.  All I've gotten, and gotten OCNSTANTLY, are friend requests for "love."  We'll see if it gets better after I not on the "hot sheet" new list.