Google’s Cookie Trick
To get around Safari’s default blocking, Google exploited a loophole in the browser’s privacy settings. While Safari does block most tracking, it makes an exception for websites with which a person interacts in some way—for instance, by filling out a form. So Google added coding to some of its ads that made Safari think that a person was submitting an invisible form to Google. Safari would then let Google install a cookie on the phone or computer.
Dean Hachamovitch (via John Gruber):
When the IE team heard that Google had bypassed user privacy settings on Safari, we asked ourselves a simple question: is Google circumventing the privacy preferences of Internet Explorer users too? We’ve discovered the answer is yes: Google is employing similar methods to get around the default privacy protections in IE and track IE users with cookies.