Having been at this for three decades has given me experience with groups at the table both as player and as a DM, that ranged from two players and a DM, up to 14 players and a DM. These experiences were in various game systems, though most were D&D.
The 14 player occasion was a single session during a Champions supers campaign that had 17 players. There was a core of fairly regular players and a host of people that just popped in now and then. I was the GM for that campaign and most sessions had from 4 to 6 players present.
I was hoping for something similar to happen with the Lost Baronies campaign, but as you have noticed if you have been keeping up with the blog, the peak was 7 players at the table (with 11 characters), and the norm seems to be two players. Lately it has been zero with cancelations happening too frequently for my taste.
I much prefer larger groups with 7 apparently being my comfort zone for D&D (Labyrinth Lord in this case). My 2nd edition game typically had 5 to 7, most often 6 players present.
The reasons I am comfortable with a larger group is not entirely clear to me, but it may be that it allows for more variety of encounters, puzzles, and types of interactions. It definitely gives everyone in the group a decent sized audience for the humorous and dramatic moments. Most likely it comes from sharing the fun with more people.
It has to be pointed out that the larger the group, the more deadly seeming an encounter can appear without breaking a certain perception of believability. There is also the benefit that one or two characters being incapacitated doesn't put the group at too great a risk of a total party kill compared to the effect it has on a smaller group.
Our weekly group recently reached a total of 9 members and the only real drawbacks from my perspective seems to be the limited amount of space which we all just fit into at that group size, and a recent spate of scheduling issues which fortunately the weekly group seems better adept at dealing with than my twice a month LL group.
Your thoughts on group size?