Thoughts provoked

The millions of people who use their cellphones daily to play games, download applications and browse the Web may not realize that they have an unseen companion: advertisers that can track their interests, their habits and even their location. Advertisers already tailor ads for small groups of consumers on the Web based on personal information. But cellphones have a much higher potential for personalized advertising, especially when they use applications like Yelp or Urbanspoon with GPS to identify a person’s location, right down to the street corner where they are standing. The capability for collecting information has alarmed privacy advocates. “It’s potentially a portable, personal spy ,” said Jeff Chester, the exec utive director of the Center for Digital Democracy, who will appear before Federal Trade Commission staff members this month to brief them on privacy and mobile marketing. He is particularly concerned about data breaches, advertisers’ access to sensitive health or finan