Combining Social Media and Email Marketing

[James]

I posted this question on the Facebook page but I thought I'd add it here as well. I'm wondering if anyone is doing anything interesting that links social media with email marketing. I know some email service providers now offer a post to social option in their email. Other companies allow you to identify which social sites an email address is registered on, how many friends they have and who their friends are. I'm wondering if anyone has used these things for marketing purposes, how it worked out, and if you have any other thoughts on using social media and email together somehow for marketing purposes.

Thanks,
James