I think the subtext here is that they're trying to speed things up, while Facebook seems to be slowing down every other page I visit by two seconds or so.
Site .facebook.com .fbcdn.net .facebook.net
Accept from .facebook.com .fbcdn.net .facebook.net
Deny INCLUSION(SCRIPT, OBJ, SUBDOC)
To be fair, isn't Facebook moving towards using iframes (similar to what this article talks about) and away from fbml - facebook markup lang?