Yeah, there's a bit of brilliance in the $10 fee for SA. It's not really enough to "exclude" anyone; virtually anyone can afford to pay a one-time fee, but if they keep getting banned and having to buy accounts, then it becomes untenable to create spam. The genius is that this didn't require teams of PhDs coming up with an elaborate Machine Learning system, it exploited the most basic of human instincts: loss aversion.

SA is just about perfect for me, since it has enough users to avoid the "dead mall" vibe, but it's still a relatively small community.