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With their recent purchase of DoubleClick, Google will be using their technology - which includes the use of the DoubleClick cookie - to enhance ad serving on your website, so they've updated their TOS to include the following phrase :
Google uses the DoubleClick DART cookie (English only) on publisher websites displaying AdSense for content ads. Subject to any applicable laws, rules and regulations, you will have the sole and exclusive right to use all data derived from your use of the DoubleClick DART cookie for any purpose related to your business, provided that Google may use and disclose this data subject to the terms of Google's advertising privacy policies (English only), and any applicable laws, rules and regulations.
A member of WebmasterWorld Forum recently started a thread on this. As web publishers, we need to keep up with changes to the Terms of Service for any ad provider we are affiliated with. This help to keep our website compliant so we don't get booted out and possibly lose a lucrative revenue stream.