Eric Tenkar has started to read an old book by Gary Gygax I've long wanted to read but have yet to track down - Role Playing Mastery.
In his first post on the subject he's talking group size, and ideal group size. Gary Gygax expressed an opinion that a fairly smallish group is ideal, but a lot of old school D&D legend is of gigantic groups and massive campaigns full of a huge rotating base of players. How true that was, I'm still not sure, but either way, for all the Mordenkainen and Robilar solo adventuring ("solo" as in "one player" not necessarily "one character") you think of RPGs as having a party of adventurers, not Conan going solo.
I started my DF campaign with five players plus one guest star (he can't commit to even our intermittent games). We ended up adding two more, for a total of seven plus one. We had a potential newbie guest star who ended up not making it. We have a line on a potential eighth player.
We've had one session that I recall with every one of the regulars there although we've been close. Usually it's closer to 3-4 players, and we've recently had a few sessions with only 2 players. Two of those, if I remember correctly, went down to one player for a while since one of them had to pop out to work in the middle of the session to take care of a few things before he got back.
I could run a game with more, but mostly we want a bigger pool because it's more fun when you've got 4 or 5 people instead of 2 or 3, and scheduling wipes out plenty of play time for everyone. We just can't reliably get that many people there. So we're always keeping an eye out for a friend we can lure back into the dungeons and who is in the right frame of mind for this kind of deliberately light game. Still, it works out to less than 5 people per session just about all the time.
So how many guys do you run for? What's your attendance rate like - lots of missed sessions, rotating pool, or play only when everyone is there?