Inform7 is a natural language based system for programming interactive fiction. http://inform7.com/

I think the following Adblock Plus filter rule would do the trick:

  ||facebook.com^$third-party

This is what you want:

||facebook.com^$domain=~facebook.com|~facebook.net|~fbcdn.com|~fbcdn.net

||facebook.net^$domain=~facebook.com|~facebook.net|~fbcdn.com|~fbcdn.net

||fbcdn.com^$domain=~facebook.com|~facebook.net|~fbcdn.com|~fbcdn.net

||fbcdn.net^$domain=~facebook.com|~facebook.net|~fbcdn.com|~fbcdn.net

The key is to allow FB's CDN when on FB, but to disallow it and everything else when not on FB.

I'm never on FB so this takes care of it nicely.

Worked a treat, cheers.