Out of burning curiousity, I contacted staff with regards to the exciting new Facebook integration feature and got told "this specific plugin isn't available on WordPress.com. However, I have just passed this along to our team as a suggestion for future updates so that we can look into incorporating any of the features that aren't currently available on WordPress.com."
I know many feel cross platform comment posting is a mess you don't want. For folks whose work thrives in a social network environment can benefit from the cross platform convenience as I've seen on a number of self-hosted WP blogs where this plugin is used.
The blog I need help with is shimworld.wordpress.com.