Whether or not they are guilty of course is a matter for the courts to decide, but it is my speculation that the search giants did not engage in creating scripts or using other poor practices to drive up traffic to extract a higher profit out of their clients. I assume that although the reasons may be intricate and complicated, one cause may lie in people clicking on an ad they had no intention of buying, just to check out the site, or perhaps sometimes by accident. The issue with PPC is that a company pays per click on their ad, not for successful conversions or on the contrary for merely appearing on the page. So they can get the same amount of clicks in one hour as in a whole week if they appear on enough of the "right" sites where people feel like clicking that day.
I know I click on sites occasionally that have paid for placement, but usually my clicks stem from curiosity about the quality and design of their site versus the organically placed sites. Maybe curiosity did kill the cat, if people like myself are personified curiosity and the pockets of these types of companies are the said feline.
I have already written one article defining PPC in which I briefly mentioned the benefits of Internet Marketing through Search Engine Optimization (SEO) instead of this lackluster ad method. Perhaps in the near future I'll write another, more in depth article on the importance of using organic instead of paid search. That way I may be able to save companies potentially interested in PPC, the search engines offering the service, and state and federal courts eventually brought into the mix via lawsuits a little coinage by steering some people away from the service.