Our D&D group meets once to twice a month and is about seven or eight people. That's large enough that at most two of us can not show up and we're still enough to play and enjoy ourselves. The DM writes session recaps and posts them the day before the next session. The overhead here is minimized by his taking notes during the session. This has kept our group going for something like three or four years now!

The one thing about D&D is that I know almost everyone there exclusively through the campaign, and 90% of my interactions with them have been in character, which means I actually know very little about their personal lives. We're getting better with this with non-D&D hangs though.