Earlier this month, Microsoft Corporation received a U.S. patent regarding "a system and process for tracking users' usage of content in computer systems." U.S. Patent No. 7,039,699 ("Tracking usage behavior in computer systems"), issued on May 2nd, claims several methods, including methods "for selectively providing content to a user", "for tracking the usage behavior of said client computer", and "for tracking usage of content at a domain level," and several systems, including systems "for tracking the usage behavior for a user of a client computer system" and "for selectively providing content to a client computer." According to Microsoft in the patent, it is "desired to implement a tracking system for computer users that does not burden computing processing, guarantees anonymity, and is applicable to track computer users navigating to various content sites hosted on various domains." This patent discloses a scenario of a client computer requesting content from a server, and in response to the request, a cookie is created and transferred back to the client computer "for future use." Then, when the client requests subsequent content, the cookie is included, and the server, upon receipt, receives the cookie and it "is processed for and updated with content usage information." In an example provided in the patent for MSN.COM, an embedded image may be used, and such an image can be "invisible." The benefit to cookies, according to the patent, is that they "provide programmers with a quick and convenient means for keeping site content fresh and relevant to the user's interests."

U.S. Patent No. 7,039,699 LINK
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Ars Technica Article: LINK