Cookie Monsters - The innocuous text files that Web surfers love to hate.

Slate.com: "Slate uses cookies. So do the New York Times, the Washington Post, and almost every media site on the net. Popular blogs like Daily Kos and Powerline have embraced them. Google and Yahoo! dispatch them to better target ads. Retailers like Amazon rely on them to fulfill orders. Even Sesame Street deploys them on its Web site.
Cookies are simply text files sent by a Web site to your computer to track your movements within its pages. They're something like virtual license plates, assigned to your browser so a site can spot you in a sea of millions of visitors. Cookies remember your login and password, the products you've just bought, or your preferred color scheme. Sites that ask you to register use cookies to target advertising�someone who claims an annual salary of $35,000 might see ads for Boca Burgers rather than foie gras. "