Recently, thanks to an invitation and some encouragement from a former student turned colleague (hi Jonah!), I've started posting "shots" of my work to a popular social media portfolio site; Dribble. You can find me here: http://dribbble.com/HatcherDesignOffice
I have mixed feelings about using social media in a portfolio context -- I have yet to create a Facebook Page for Hatcher Design Office, and I am very careful about the work I submit to Dribble. I'm not alone in this conundrum, either. I've read several articles, including one from the AIGA, and talked to many other creatives and it seems like we all have a love-hate relationship with the idea of sharing.
On the positive side, social media presents an opportunity for easy and effective self promotion and connection with both colleagues and clients. In an ideal context this would lead to more business and more effective creative progress -- a win for everyone.
On the negative side, exposure raises legality issues when "previewing" active client work; it also leaves one's work very open to the potential of mimicry or being stolen outright. Nor can one forget the ultimate creative blasphemy of crowd-sourcing, which completely vilifies social media in the context of creativity and the worth of the work. See this article from the Forbes' blog about Gaps' failed attempt to crowd source a solution to its 2010 logo fiasco.
For now, I think that the solution is to forge ahead and push the creative and the business a bit further into the connected world -- but cautiously. I won't be posting work in progress and I'm still not ready for the "shameless self promotion" of a FB fan page, but I am ready share some completed work more openly, and I am really looking forward to feedback from new places.