Karen, here's Dave's response on a different thread:
"I do not publish the algorithm that causes a person to be banned from a specific forum due to red-icon reports...
But also, I personally investigate all reports that are entered in, and find spammers that way. When a number of people report a spammer, I see it, and I go ahead and ban them from the entire site. That part is manually done by me."
I read that to mean enough red reports will ban a spammer from a specific forum automatically, but then Dave manually bans the spammer from the entire site.