europeforvisitors - 1:35 am on Dec 13, 2003 (gmt 0)

I think the risk of competitors clicking on your ads is somewhat overblown, because they are exposing themselves to significant risk without having much to gain...

A bigger problem could be advertisers clicking on their competitors' ads. Of course, that could happen with AdWords, too, not just with AdSense. (In fact, it might be more likely to occur with AdWords, because it's probably easier for an advertiser to find its competitors' ads on SERPs than on third-party content pages.)

As for why AdSense accounts get terminated, any number of factors could come into play. For example, if a site seemed especially prone to "click vandalism" because of controversial subject matter or a hotheaded audience, Google might figure that it would be easier to close the account than to investigate fraudulent clicks over and over again. (I'm not suggesting that this is desirable, by the way; I don't think it is, but in a business environment, decisions are likely to be driven by dollars-and-cents issues.)