While I'm sure Yahoo! will come up with a very plesent sounding reason for tracking every webpage I go to, but personally I find it really freaking insane.  Yahoo claims to not share "personally identifiable information" which I find laughable as the webpages you click into are just loaded in mass into a database and then sent off to ... who knows?

Just to be fair, Yahoo is hardly the only one using web beacons (see below), but if you are a member of any YahooGroup, if you are logged in right now or not you can opt out on each machine by going to http://privacy.yahoo.com/privacy/ and then about half-way down the page, in the section on cookies, you will see a link that says WEB BEACONS, and you have to dig around until you find this ---> http://pclick.yahoo.com/p?optout

Web beacon, also called a Web bug or a pixel tag or a clear GIF. Used in combination with cookies, a Web beacon is an often-transparent graphic image, usually no larger than 1 pixel x 1 pixel, that is placed on a Web site or in an e-mail that is used to monitor the behavior of the user visiting the Web site or sending the e-mail. When the HTML code for the Web beacon points to a site to retrieve the image, at the same time it can pass along information such as the IP address of the computer that retrieved the image, the time the Web beacon was viewed and for how long, the type of browser that retrieved the image and previously set cookie values.