Click Fraud

Anyone using Adwords or Yahoo Search Marketing has probably heard of "click fraud".

"Three times as many online advertisers and search engine marketing (SEM) firms said click fraud was a serious issue in 2005 compared to the year before. Of the 553 respondents to SEMPO's December 2005 "The State of Search Engine Marketing" survey, 16 percent of advertisers and agencies say they are tracking click fraud, and agree it's a significant problem."

http://www.clickz.com/news/article.php/3587696