Virus Writers Taint Google Ad Links
Virus writers have been gaming Google's "sponsored links" -- the paid ads shown alongside search engine results. They are aiming to get their malicious software installed on computers whose users click onto ad links after searching for legitimate sites such as BBBonline.org, the official Web site of the Better Business Bureau
http://blog.washingtonpost.com/securityfix/2007/04/virus_writers_taint_google_ad.html
http://explabs.blogspot.com/2007/04/google-sponsored-links-not-safe.html