Google will begin tracking users' interests and shopping in an effort to allow its AdSense customers to provide targeted advertising.
But the privacy implications of the new system look set to draw the interest of privacy advocates and legislators.
The new feature, which Google calls interest-based advertising, will track users' web browsing and shopping habits and build a group categories of interests based on this history, the search firm said.
To assuage the privacy concerns, Google offers the ability to opt out. The opt out information is stored on a cookie which will be cleared if the cookie is deleted.
Users also will be able to edit the categories of interest associated with their browsers via the new ads preferences manager.
Google has pledged to be transparent in regards to how it collects and uses the information collected.
All Things Digital columnist Peter Kafka believes the move will make Google a target of US congressman Rick Boucher, chair of the house communications subcommittee, who has already called on congress to regulate the practice of interest-based advertising.