Abuse

Some webmasters create websites tailored to lure searchers from Google and other engines onto their AdSense website to make money from clicks. These "zombie" websites often contain nothing but a large amount of interconnected, automated content (e.g., a directory with content from the Open Directory Project, or scraper websites relying on RSS feeds for content). Possibly the most popular form of such "AdSense farms" are splogs (spam blogs), which are centered around known high-paying keywords. Many of these websites use content from other websites, such as Wikipedia, to attract visitors. These and related approaches are considered to be search engine spam and can be reported to Google.
A Made for AdSense (MFA) website or webpage has little or no content, but is filled with advertisements so that users have no choice but to click on advertisements. Such pages were tolerated in the past, but due to complaints, Google now disables such accounts.
There have also been reports of Trojan horses engineered to produce counterfeit Google advertisements that are formatted looking like legitimate ones. The Trojan uploads itself onto an unsuspecting user's computer through a webpage and then replaces the original advertisements with its own set of malicious advertisements.