How many people need to use Report Spam?

I know there's a minimum needed for an account to be automatically muted/banned, and don't expect that number to be given out. What I'm looking for here is - does every single use of the tool get looked at? Or do a certain number of people need to use it on a spammer before they're brought to the GMs' attention at all?

http://i55.tinypic.com/s5v2hv.jpg is why I ask (name of everyone in trade is edited out, know about the no-calling people-out thing). Not counting the guy selling gold, there were only 17 people in the channel - and I would imagine that not everyone was actually paying attention at the time, or would bother to use the tool if they were.