I don't know that the group was "contained" to begin with~!
In theory, and what was initially the goal of BYOC was to assist and facilitate people hosting poker games. This spawned the discussion board which allowed people to post their games, discussions, etc. etc.
There is nothing that says this is a closed group. If someone wants to host a game, go for it. If there are other games that night, so be it. Some will host at certain stakes, and others at their preferred stakes / format. There are also those that play that more than the others in the group. Some play once a month, once a week, and others multiple times a week.
Nobody runs BYOC, (other than my fronting the bill for the server / connection to maintain the web site), we are simply a bunch of guys and gals that have poker tables and enjoy either taking money from someone or giving it to someone else.
What has turned out is now those that prefer one buy in / format, versus a different buy in / format. I play in a couple of other games / groups that have the same dynamics of BYOC, which is pretty much "to each is own", different people, different hosts, different games.
If something were planned out far enough in advance, I would love to see a 60 or 70 person tourney / gaming event that brought everyone in the same room.