AFAIK there was always this friendly rivalry? Dunno. I was initially registered on DAC before migrating to NMA because even back then it seemed like a very closed community, similar to The Order over here, but it was the whole forum.
Sounds about right. For one thing I'd say the sites had pretty differing stances on administration and moderation, and because of that different kinds of posters sort of naturally gravitated toward one or the other site. The members and the moderators together define the forum content, and over time that in turn makes one of the forums seem preferable over the other to newcomers, and so it becomes some kind of a feedback loop. Or some shit like that, that's just my theory. It's perhaps worth a mention that DAC's forums were very mild-mannered way back in the day when DAC was hosted by GameSpy but started becoming more and more temperamental after the migration from V13.net, the creation of a certain anything-goes subforum and due to some changes in administration; whether this shift was for better for worse is a matter of taste I suppose. Anyway I don't mean to turn this into a history of DAC thread, I just find it interesting how the sites seemed to cater to different crowds despite both being Fallout fansites and how little overlap there was, besides the shared disdain for Fallout 3. [EDIT: the #fallout IRC channel did bring some of the people from different forums together, but I'd say for the most part both parties kept to themselves]