Paul Briant at the Reluctant Blogger came up with a doomsday scenario: if Microsoft upgraded Windows (or perhaps IE) with a text-ad-blocking feature turned on by default, it would be the end of Google as we know it. Unlikely for a variety of reasons, but not impossible, considering that a pop-up killer is a standard option on most browsers now, and that there's third-party software that zaps AdWords as well. Also see the comments on 25hoursaday: "The outrage from Google would be tame compared to how pissed off all the companies that depend on AdSense and Adwords would be." It would also put the anti-MS and pro-Goo crowd in a peculiar position of having to turn the adblocker off to spite Microsoft.
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