It's a free internets. Obviously it's inappropriate to advertise the splinter forums on GAF, conflict of interest, and of course when people from those sites do or attempt to do nasty stuff to GAF or GAFers that's not cool, but otherwise, *shrug*. Everyone needs a place to be, and some folks get banned here or don't like it here.
Those Rock Band guys who weren't trying to spam GAF but felt threatened by the Rock Band OT changing and lashed out and got permed too, I mean, megathread policy changed and that was that, if you don't want to follow the rules here then by all means go elsewhere, I even suggested as much. Could I have been more diplomatic? Yeah, but it was pure antagonism from the start when I posted in the Rock Band OT. Should I have addressed the megathread situation sooner so that things wouldn't have been nearly so messy when policy did change? Absolutely I should have, but I addressed it when I did and dealt with the mess as best I could.
Nowadays when a popular insular subcommunity forms and people get really attached to it, I try to give them a place in the community forum (see: Ausgaf, Ponygaf). That's about the best I can do to keep the main forums running smoothly and not be too disruptive to those social structures.