Ads Follow Web Users, and Get Much More Personal

For all the concern and uproar over online privacy, marketers and data companies have always known much more about consumers' offline lives, like income, credit score, home ownership, even what car they drive and whether they have a hunting license. Recently, some of these companies have started connecting this mountain of information to consumers' browsers. The result is a sea change in the way consumers encounter the Web. Not only will people see customized advertising, they will see different versions of Web sites from other consumers and even receive different discount offers while shopping — all based on information from their offline history. The technology that makes the connection is nothing new — it is a tiny piece of code called a cookie that is placed on a hard drive. But the information it holds is. And it is all done invisibly.