NY Times: Who Do Online Advertisers Think You Are?

By JEFFREY ROSEN Published: November 30, 2012 in The New York Times

Not long ago, I decided to test how much privacy I have online. I cleared the cookies, the bits of code that Web sites leave on my computer to track what I browse and buy, from my two Internet browsers, Safari and Firefox. Then, with my digital past superficially erased, I set out to create two new identities: Democratic Jeff and Republican Jeff.

Having created my new digital identities as heavy-handedly as possible, I returned to my usual Web sites. At first, the ads on my favorite Washington neighborhood blog, the Prince of Petworth, were the same on both browsers. But less than two days later, an ad for Mitt Romney suddenly appeared next to a story I was reading on Firefox about Gore Vidal's burial. When I opened that page on Safari, the ad in the exact same spot was for Catholic University's master's program in human resources management.