Retargeting Ads Follow Surfers to Other Sites [New York Times]
Have you ever had the experience of shopping on the web at a particular site, then later noticing that web ads from that retailer pop up on other unrelated pages? The New York Times has profiled the practice of behavioral-based advertising, where companies like Microsoft and Google, which run large ad networks use information captured from third-party retailers to send related ads to users.
These targeted ads are frequently achieved by the use of information about a user's browsing habits that are stored in cookies. Normally that information is only accessible by the site that created the cookie, but using so-called "third-party cookies" a user's browsing history can be shared across sites. So if you go shopping for a new car on an automobile manufacturer's web site, you might see new car advertisements popping up on an unrelated web site thanks to third-party cookies.
While some users find these targeted advertisements more helpful than non-specific ads, others are concerned about the way these ad networks can store their personal web browsing history. The Times article notes that lawmakers in Washington are aware of the practice, and are considering various legislative alternatives to regulate how web sites use behavioral based web ads.