ecamber: As much as the GOG forums are in dire need of some technical updates, I really hope that they don't make drastic changes that ruin the feel of this place. I've seen too many forums switch to new "better" technologies only to find that the old system actually better suited their community.
If anything, a traditional forum would help this website a lot. As it stands now, threads and "discussions" pretty much just vanish into the big nothingness. It sure doesn't inspire users to engage with each other.
Anyway, as for forums: GIGA (forum pretty much died with the channel going off-air) and Travian (they never properly made the switch to (or the addition of) mobile in a smartphone-dominated world, so the forum slowly died out, as interest in the game waned). Apart from those, forums where gaming was only secondary: AFF (decreasing interest in forums over time + off-time for over a year killed it), Hongfire (hackers, law enforcement - although it still exists in one form or another).