BF, to me, sounds just to... not real decent, let me explain:
This sort of name would of done wonders for TfT or RoC, where you could only use up to 4 letter, and could look in the players profile for the full name, and see "Battleforums." Well in WoW you're going to be running around all over the place with "bf" under your name, it just doesn't look proper, you understand where I'm going with this right? Just having "BF" under ones name might feel... "inadiquet or imcomplete" with just an addbreveation. As apposed to having something like... "Brotherhoods of Battleforums" under it.
I suppose the point I'm trying to make would be, use something more original then an abbreceation, in the spirit of the game, something people would understand.
I'm done. I just had to get out my distaste in having an abbreveation for a guild name, to hear one final piece of input...