FB is now making it possible for other sites to comment on your FB via syndication, if you choose to allow it, similar to
Disqus. Initially, it looked like google and twitter were both on board... now, it is questionable. Yahoo id's will be linked for now.
If you are unfamiliar with this, basically, let's say you post about a movie on your FB, which also is the same post information as on your blog, someone could now comment at the blog and this will syndicate to the FB and vice versa.
More information and to use now, go to
Tech Cruch.
The newly overhauled Facebook comment system