How do I get a backlink from twitter and facebook

Will just posting an update on my fan page and tweeting the link out get me the high PR backlinks. Is it that simple?

Twitter is nofollow (apart from the link to your blog in your profile). However, tweeting does get you indexed fast, and occasionally when your stuff gets retweeted it shows up in some twitter aggregators which are do follow. Should you bother? It depends on how much time you have, to be honest. Tweet when you set up your site to begin with, and then move on to better more beneficial backlinks.

Facebook - the public fan pages are do follow, but am not sure anyone has gotten an SEO benefit and ranked due to posting links on Facebook. Facebook is mainly there for social proof. But if someone has ideas to contradict this, I'm open to persuasion.