Is it just me or does it seem like banning people for that is a stupid idea. I can understand the concept behind it - ban people who spam to get traffic. HOWEVER, there is a little problem with that idea. The main idea is that you don't know who is posting those ads! How is Google suppose to know if it was the webmaster who posted them or a competitor who is trying to get rid of some competition. The same thing could be done by using paid traffic services. Just sign your competitor's websites up for 100,000 hits and poof, watch their adsense account get banned. Is it just me or is banning people for bad traffic a bad idea? What google should be doing is analyzing where the traffic is coming from and if it is bad traffic then simply give 0.00$ for each click that is received from that traffic. That way paid for traffic is pointless as well as spamming places like craigslist!
Well... If you are getting 100,000 hits and low click wrt to those hits then adsense will sense some foul play.. For example take stumbleupon. Sometimes it send great, unusually high traffic, with just no effort on our part, but most of these visitors are not the kind of who will click on ads. So eventually the ads CTR drops down. If this continues for several days then i think adsense flags your account for keeping an eye on traffic behavior. I think there may be many techniques by which google finds out spamming... not just by checking IPs but they use cookies, and god knows what else technology do google use.... you can always report to google support if you think someone is spamming your site and you are getting unusually high traffic and low adsense clicks.
It's against the google TOS, but they don't have any real way of knowing you are spamming unless a craigslist user reports you. Spamming craigslist is also a terrible way to get traffic.