Criticism

Due to alleged concerns about click fraud, Google AdSense has been criticized by some search engine optimization firms as a large source of what Google calls "invalid clicks", in which one company clicks on a rival's search engine advertisements to drive up the other company's costs.
To help prevent click fraud, AdSense publishers can choose from a number of click-tracking programs. These programs display detailed information about the visitors who click on the AdSense advertisements. Publishers can use this to determine whether or not they have been a victim of click fraud. There are a number of commercial tracking scripts available for purchase.
The payment terms for webmasters have also been criticized. Google withholds payment until an account reaches US$100, but many micro content providers require a long time—years in some cases—to build up this much AdSense revenue. However, Google will pay all earned revenue greater than US$10 when an AdSense account is closed and not disabled.
Many website owners complain that their AdSense accounts have been disabled just before they were supposed to receive their first paycheck from Google. Google claims accounts have been disabled due to click fraud or forbidden content, but have offered no proof of this. An automated email is sent to the publisher's owner which offers no reasoning, or options but a link to file an appeal. In the email, Google states that "Because we have a responsibility to protect our AdWords advertisers from inflated costs due to invalid activity, we've found it necessary to disable your AdSense account. Your outstanding balance and Google's share of the revenue will both be fully refunded back to the affected advertisers." The revenue generated - whether legitimate or not - is taken, and all complaints are deferred.
Google came under fire when the official Google AdSense Blog showcased the French video website Imineo.com. This website violated Google's AdSense Program Policies by displaying AdSense alongside sexually explicit material. Typically, websites displaying AdSense have been banned from showing such content. Some sites have been banned for distributing copyrighted material even when they hold the copyright themselves or are authorized by the copyright holder to distribute the material.
It has been reported that using both AdSense and AdWords may cause a website to pay Google a commission when the website advertises itself.
In some cases, AdSense displays inappropriate or offensive ads. For example, in a news story about a terrorist attack in India, an advert was generated for a (presumably non-existent) educational qualification in terrorism.
AdSense sets tracking cookies that are viewed by some as a threat to privacy. Webmasters that use AdSense must place the appropriate warning in the privacy policy page.