Didier Stevens is a computer geek who likes to push the envelope. Six months ago he bought a Google AdWord campaign and made an advertisement that said if your PC was virus-free you could get it infected by clicking the ad. The ad made it through Google AdSense policies and was displayed more than 230,000 times and received 409 click-throughs from folks who attempted to infect their computers through a Google ad.
Implications - The actual ad that Didier Stevens created reads, "Is your PC virus-free? Get it infected here!" The people who clicked on the ad didn't actually receive a computer virus. Stevens was surprised that Google even let him put the ad on the Internet in the first place because of their security.