The crappy forums don't have to let anyone register without a vouching process if they don't want to. They also don't accidentally end up on the Reddit Front Page and get swarmed by a mob of overly-enthusiastic or angry strangers who don't know or follow the community's etiquette.
> They also don't accidentally end up on the Reddit Front Page and get swarmed
Wouldn't this by definition mean the size of the community must always remain small enough (whatever that magic number is)?
Valid points. I was never a member of any forums with closed, invite-only registration, and I've never been part of a reddit community that had to deal with front page traffic or brigading, so I sort of assume this is the median experience.
The maker communities, music subs, and local/city subs I'm in do not have any of these problems.