BFD was supposed to be a joke on two levels.
First, Aegon mistakenly posted "Barristan freakin Dayne". He either meant Barristan freakin Selmy or Arthur freakin Dayne... but it came out Barristan Freakin Dayne. BFD. Second, in the U.S. we sometimes use acronyms, actually we love acronyms! BFD is used to show how little or how much we care about something. It comes from Big Freaking Deal... except we don't mean freaking, we mean the Queen Mother of dirty words. You could use bfd like this, "John got an IPod for Xmas? BFD, I went to LA."
BFD is not to mistaken for BFE. BFE means some place far away... as in Bum Freak Egypt, but again we don't mean freak, we mean the real deal. You could use bfe like this, "Dude, sorry I'm late. I can't belive the crowds. I had to park in bfe.
The best satire I can recall of Americans love of acrostics is in Good Morning Vietnam. Robin William's character takes this to an all time high.
I have no idead if other cultures do this to the extent that we do. Yes, I know this is not the forum or thread to have this discussion.
So to stay in proper form, I'll finish by saying "Go AFD!"