I've been waiting for this to occur. Business Week takes on what they call the "dark side of online advertising," click fraud. A reasonably thorough article with some specific, "this happened to me" stories. I'm still puzzled by the hustle to move everything to a web-service with money based on advertisting (I know not every web service goes this way, but most have at least an eye on that model) when we have a culture that, in general despises advertising of any stripe. But yet, onward we go as we stick ads on this service and that. Sooner or later click fraud, or some other type of fraud, is going to lead to a bigger bust than the previous one.