Click Fraud
Click fraud comprises clicking on a link that either provides monetary gain for the clicker or adds cost to the marketer whose link is being clicked (a competitor of the 'clicker' for example). This process can be automated. This causes problems for links that are based on a PPC model, and is thus a problem for search engine advertising programs and affiliate programs. The problem is compounded in search engine marketing as the host, who manages the advertising programs, actually benefits from the rogue behavior.