Advertising abuse and click fraud might sound benign, but they can cause significant damage.
Click fraud occurs when bots are sent to “click” on ads; it can skew the results of a commercial or political ad campaign. The direct victim is the advertiser who invests poorly and spends the ad budget in the wrong places. The site hosting the ads (and not properly controlling bot traffic) is harmed later when the network blacklists it.
Advertising networks can be quite aggressive about blacklisting sites that have inadequate bot control. Otherwise, their advertisers slow down or stop their campaigns due to a failure to receive worthwhile results (despite getting lots of “clicks”).
Fraudulent clicks from bots often result in reversals of payments that were made earlier by the ad networks. For the site that hosted the ads, this results in loss of revenue. This loss is irrecoverable, because those page views are in the past, and the opportunity to receive ad revenue from them cannot be repeated. Further, if the click fraud is not brought under control, the networks will eventually refuse to supply ad inventory to the victim’s sites.