AdSense~Criticism

Due to 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 ads to drive up its costs. Some publishers have been blocked by Google, complaining that little justification or transparency was provided.

To help prevent click fraud, publishers can choose from a number of click tracking programs. These programs will display detailed information about the visitors who click on the AdSense advertisements. Publishers can use that data to determine if they've been a victim of click fraud or not. There are a number of such commercial scripts available for purchase. An open source alternative is AdLogger.

Google has also come under fire for allowing AdWords advertisers to abuse trademarks. In 2004, Google started allowing advertisers to bid on any search terms, including the trademarks of their competitors.

The payment terms for AdSense customers have also been criticized. Google withholds payment until an account reaches US$100 , but many small content providers require a long time - years in many cases - to build up this much AdSense revenue. These pending payments are recorded on Google's balance sheet as "accrued revenue share". At the close of its 2006 fiscal year, the sum of all these small debts amounted to a little over US $370 million - cash that Google is able to invest but which effectively belongs to its customers.