In a traditional group or forum, you may only know 10 people after a year or two. But in a monthly group of 10 people, that number increases to 9 x 12 people.
One of the biggest challenges of traditional forums and groups is that not everyone has something good to say. With many people, there's a tendency to be "lurkers" or "likers" rather than active participants. But when you're put in a group of 10 people, your desire to express is likely to be satisfied because you don't care much about
You may not have realized this, but traditional groups and forums revolve around a few moderators because they are more willing to share or have more to share. But is this the best form of community? I don't think so. It's possible for a community built by a random group of 10 people per month to become an extremely active community!