My current crop of regular gamers - in DF Felltower and in AD&D, and in andi's GT game as well - consists of a lot of people.
How did this happen?
We started with five, only four of whom could make the first session. They were guys from my previous gaming group and a friend who'd popped in and out of my games for years.
Over time, we added two more online acquaintances. We lost a couple of the originals over time. Then we added back in two guys from my previous game. Then the son of one of the players began to play, at the same time as a new acquaintance tried the game. Then his sons joined in. We lost one to "occasional only" status due to work, and another dropped out after the big Beholder fight, coincidentally or not. One guy who popped in for GT became a semi-regular in DF and in GT, and plays AD&D with us sometimes, too.
This has left us with nine regular players not including me, and a couple of occasional players.
It's why I'm reluctant to add players even when people have asked. Returnees are always welcome, though. Potentially, we could have a session with 14 players if everyone came back.
The benefits and difficulties of size have really been apparent, recently.
The sheer physical size of the group means that if a lot of people can come to game, we need a lot of room. A table with a folding table on the end, with the GM trapped in a corner, is standard these days.
We can't easily run games balanced for a smaller group. Have a D&D5 adventure set for five gamers? We're going to double that.
But we can run really old-school tournament adventures no problem. Nine PCs like in the A-series and G-series? No problem. We can take a solid crack at the 20-man roster from Tom of Horrors or Barrier Peaks with only one or two people needing run a third character. Maybe with some running only one if we get an especially full house.
It's bad for my love of henchmen and hirelings. I wrote DF15 and it gets less of a workout in my GURPS games when people show up with 8-9 PCs to explore 3-yard wide dungeon corridors.
It's good for running games in general, because we only need 3-4 people to play the game with a solid base of adventurers, and that means any day we choose is good enough.
It's bad when we have no idea if we'll have four or eight on a given day, though.
Games can be slow - and combats even slower. If everyone takes 1 minute to resolve their turn, a 9-player roster takes an hour for a 6-turn fight - and that assumes the GM can get through all of the NPCs in 1 minute! I've needed to offload some of the responsibilities to coordinate big fights to the players just to keep up.
Overall, it's a plus. I get to run big games, and there is no one in my group that I'd be happy to see leave. I'd be even happier if the ones who can't come regularly or who quit long ago were able to come back. But it's not without complications and benefits.