Yeah Mafia has a lot of spam in it; people, myself included, have been treating it like we would user notes until the staff decided what direction they wanted to take with the groups. If it does stay and there's a problem with spam then I'll clean it up and crack some skulls if it carries on. No big.
I personally don't have a problem with what you see as spam, though, and I wouldn't have a problem with it if the Moebetics crew did it either. Maybe others disagree.
But as Mafia at EoFF is more of an event that requires organisation as opposed to "Hey look, cute Japanese things!", that's why it is more likely to stay.
I don't see how the regional groups have any significance at all, because there are meetup threads all the time regarding specific locations.
It's not just about big meetups though. It could just be for a couple of people hanging out, which happens a lot more often than large meetups do anyway.