Comment by buro9

These are the AdBlock Facebook rules 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.