Facebook's privacy is bad and here is more proof.
How to get those comments ? Simple using the open graph protocol , and a simple query you can rip all the comments.
Here is the code :
https://graph.facebook.com/comments/?ids={the url here }
Demonstration
Ripping comments from TechCrunch :D
https://graph.facebook.com/comments/?ids=http://techcrunch.com/2011/03/01/pros-cons-facebook-comments/
I am currently using facebook Comments , let's see how it goes!
Blogger Comment
Facebook Comment