So, for reasons that god only knows, I've spent the past ten minutes thinking about a hypothetical situation in which all threads were unable to be locked, and toady couldn't moderate.
If we assume that something may split the bay base, it's easy to tell where most people might retreat to, the lower boards (Forum games and roleplaying, specifically), while small and with a dedicated base, that particular area is easily disrupted and players there would be easily shocked by spam images, a quick rush towards there could probably make a strong foothold and push quite a few people out of there, once people more experienced with the art of forum warfare have become established, however, it would be a formidable defensive position, allowing quick strikes then sudden retreats back into the shell.
The Mafia subforum, however, poses a bigger challenge to wedge long time players out of there, while few in number, the ones that do frequent are hardened against anger and salt, not to mention the mafia games normal time-frame, so any attack that could have shaken a FG&R user would simply be brushed off by a mafia player, though the natural tendencies for the long and thoughtful mindset mafia inclined players have would make them far more defensive than other subforums, to a point of being almost completely neutral, these ones would probably last the longest.
Roll To Dodge, however, might be a wildcard, most RTD's are minimalistic and are based around bat-shit insane actions flying at top speed, the candle that burns twice as bright, lasts half as long, as they say, any attacks against them would most likely end up with a fierce counter attack, thus giving others natural disincentives, the ones that aren't minimalist would be well protected simply by proxy, and I could think of very few people who would turn on their own front to focus on something like Life Begins At Death, yet they would most likely burn our soon, any attacks made by them would rely on shock and awe, sort of like a blitzkrieg, otherwise, they would probably peter out fast.
ER, now that's a tough one, the lack of dedicated players is quite nicely balanced out by the sheer strength of the subforum itself, it would be easy to overlook given it's small profile while anyone trying to disrupt it wouldn't get much even if they did succeed, as unlikely as that would be considering the sheer lumbering strength of the GM, Piecewise, and his unstoppable power that is ER itself.
I can certainly see general discussion being hit the hardest, it's sort of a middle ground between FG&RP and dwarf fortress discussion, easy to target, and can give a lot of power, it may be the biggest battleground around this forum.
Oh man now I wanna make a forum game about a forum war, but more dramatised, not just posts, it's a warfield! Trololos flying overhead and detonating in shrapnel fields of U MAD BRO? While Spooky Scary Skeletons act as the cavalry charge to the forum battlefield, scattering forces simply from the spoopyness.