Last week Facebook added the "Subscribe" button and feature to their social offering. There is talk there will be more buttons to come. Read,Listened,Watched and Want according to a source are next.
WordPress.com has unveiled the "Follow " button. It will be at the bottom of all wordpress.com blogs in an effort to increase traffic for WordPress.com bloggers.
Full story can be read at http://en.blog.wordpress.com/2011/09/21/more-traffic-for-your-blog-with-the-follow-button/