This is scary. Google is adding interest-based advertising, going a step beyond the targeted advertising they now offer to Adsense advertisers. Google will track actions across the Internet in order to serve interest-based advertisements to users.
Although it sounds good in theory, this is behavioral targeting. Google has indicated that there will be an opt-out option, IF you know to ask for it. For a majority of users, their actions will be cataloged, their market segment determined, their demographics noted, and their privacy violated.
For related posts about behavioral targeting, click here.