Interest-based advertising will allow advertisers to show ads based on a 
user's previous interactions with them, such as visits to advertiser website 
and also to reach users based on their interests (e.g. "sports enthusiast"). 
To develop interest categories, we will recognize the types of web pages 
users visit throughout the Google content network.  As an example, if they 
visit a number of sports pages, we will add them to the "sports enthusiast" 
interest category.