Humans are social beings. We’re hard-wired to lean on each other and form alliances.
I belong to several groups, and the dynamics are all very different.
My studiomates are our own little micro-community of friends. We do more than just get along. We have this unspoken bond, and we genuinely care about each other.
My local vegetarian/vegan group is much larger, and much less personal. I feel like we are obligated to socialize because of our location (KC), shared ethical beliefs and similar diets.
I feel like the size and circumstances of a group definitely affects how people feel about it and interact with it. Groups are more effective when people care. They are even more effective when there are similarities between the people involved.
The strongest and largest communities somehow evolve into subcultures, and individual personal convictions become less important. Those groups are vastly different from small niche communities, and their dynamics are less like ripples and more like waves. Larger groups make more of an impact, but the subtleties can be lost. And smaller groups are incredibly varied and full of personality.