Sensible, but short, article on the cross-over between email marketing and social media. I think "do it" is the best summary:

* Archiving email newsletters online and posting links to them on Twitter, Facebook, or LinkedIn can extend the reach of that communication
* Including links from blog posts or YouTube videos in an email newsletter can encourage subscribers to explore new social media efforts
* There are easy ways to add newsletter subscription links to social sites through blog badges, Facebook applications, or HTML