In September, Facebook introduced Subscribe to make it easier for people who want to share their public updates with more than just friends to build an audience of subscribers. Today they’re launching the Subscribe button for websites, a social plugin any site can add to give visitors the option to subscribe to contributors in one click.
How It Works
The Subscribe button for websites works just like the button on Facebook; once clicked the user will begin seeing the public posts of the person they have subscribed to in his or her News Feed. The subscribe action is also shared -- allowing others to subscribe directly via the News Feed stories, and further increasing viral distribution.
More informaion can be read at Facebook