There's a thread for the Big Forums so here's one for us.
I have several boards and each have only 100 members or a bit less. That's intentional, not because I want it bigger but can't do it!
One of mine is an online tutoring project and we found that getting bigger just makes our students a list of names. Our services are for young people who have been bullied or have health issues so they need to get real personal attention. The tutoring forum itself is not listed anywhere for privacy reasons..
The public site for this project is www.firstcollege.co.uk It's XF but simply usinmg it as an editor so I'm the only member.
Another board I do is a personal community of free thinking people I have collected over the years. We hold events in the UK and focus on strong mutual support as a Clan. Again this would dilute if there were lots and lots of members.
Maybe my sites are really unusual in being so deliberately small. Just thought I'd put out the call and see.
There are interesting issues making "microforum" management different.