Behavioral targeting will now be available to all Adwords users, which was a feature long-in-waiting for many advertisers. The search giant first launched a BETA version of this tool back in 2009, but made it available only to small groups of advertisers--until now.
The new functionality will allow advertisers to select audience based on interests based on their browsing activity or online behavior. More specifically, the tool groups users based on the types of pages that a user visits. The tool considers how recently and frequently the user visits those websites or web pages. Using identifying browser cookies, users can be targeted by advertisers of specific categories. Currently the program supports about a thousand categories, and the functionality has been shown to increase ROI.
There is also an opt out function for the user--should they not wish this extra level of tracking.