Sure. The social media circus does nothing but create personas. There are ways to use it properly, but not without ensuring complete privacy in a closed discussion group.
The biggest problem I see right now is that Facebook is selling advertising to get more likes. People like whatever page is shoved in their faces and then they don't really do anything with the page.
But there are a few things I have seen work. One of them is the networkedblogs application.
You can keep your readers posted, but it would be a lot easier with a simple newsletter.
It took me a long time to actually get Twitter to work for me, but in time I have gotten a few followers which actually read one of my blogs and are interested in the specific content which is a not much talked about niche.
So there is a difference between targeting keywords people are already searching for and bringing something completely new to their attention.
For the latter I recommend social media.
For anything else, SEO and PPC is the way to shove away the pre existing competition.