eWeek: "Rogue anti-spyware software that pushes fraudulent PC scans has found its way onto DoubleClick and legitimate sites, including CNN, The Economist, The Huffington Post and the official site of the Philadelphia Phillies."
Earlier:
Banner Ad Gone Phishing
Evil Ad Tech, Part II
Future: Talking Ads Take Over Computers
Subliminal Spam
DIY Submilinal Messages
Ads Means Worm
Hijacking MySpace Pages