I did an article a while back that shared a part of an interview between Matt Cutts and Eric Enge, where Matt highly endorsed Social Media Marketing as a quality link building method.
Matt Cutts: Whenever you pay money to a social media consultant to try to show up on Digg, you are not paying for links. You are funding some creativity; you are sponsoring your page for some creativity.
It’s not like you held a gun to anyone and said “Okay, you have to link to me”. The people who link to the site are linking because it’s something compelling instead. So, there is still some editorial choice there.
It was nice to see that Google’s feelings on social media have not changed, as in the interview with Rebecca, Matt didn’t even have to be asked before mentioning that ‘good social media with high quality content is certainly a good way to go viral’ and get links.
He goes on to say that Google ‘hasn’t really had any problems with social media as you normally have good stuff that then gets editorial votes (aka links) which is what you want’