Sites like Trulia, Zillow, etc. aren't social networks (since there's no hierarchical structure of connectivity between members) but are effective tools of engagement.
I have had 3 hits on my website from zillow in the past thirty days, I have inly posted there 20 times. I just became an allstar, nice badge but they should have just cut me a check.
I have had 3 hits from active rain in the past thirty days, probably agents.
I have had 10 hits from my twitter profile link to my website in the past 90 days but I can see that the real value in twitter is retweet, If I post an interesting blog and ask people to retweet then the number of visitors to the blog increases and with a link on my website traffic skyrockets compared to just blogging.
Here is a series of events, Blog, tweet the blog, ask people to retweet, push the blog on digg etc, reblog on activerain, wordpress etc... Do a video about the blog, tweet, retweet, repost ...oohh I am starting to get dizzy
I think Youtube is where I am going to explode, You can track when your videos are watched and where that person is located if available. They also have a graph so you can see which of your videos is popular and the rise and fall of popularity. You can also pay to advertise your videos, I pay .25 a click and haven't gotten to many clicks but the value there is that when you pay to promote they allow you to put a call to action on your video. For example at the end you could put fill out an application now and post a link to your website. Most sites allow you to embed the video, so it is reblogable (yes I think I just made that word up).
I use social media all day long you can find me on twitter, Trulia, Zillow, Fizber, ActiveRain, linkedin, blogtalk radio(soon), mybloglog,Mortgagefit, facebook, you tube, five blogs, three blog discusion forums some other places I can't remember right now.
I also use email campaigns to keep me in front of people I have done business with in the past or could do business with.
I receive updates on my blackberry so I can respond promptly, if some emails or clicks contact me on any of the forums.
Out of all of the sites I get the highest quality of leads from Trulia.