OK, you can take your tinfoil hats off now. German site Heise Online has tested Hackint0sh user XianLi's claims about the iPhone sending its IMEI to Apple while accessing the web. According to Heise and other sources, this is not true:
While the code says "IMEI," which stands for International Mobile Equipment Identity, it seems that the actual IMEI is not transmitted. Using a sniffer, Heise says they were able to get the information that the applications are actually sending. The strings aren't the same as the test iPhone's IMEI and, in fact, each application sends its own unique code.
According to further testing by Rene at blog docpool, these IDs are identical in all iPhones he has tried. The most plausible explanation: the codes could be just application identifiers. Rumor smashed. Mystery solved. Time to get a bourbon at Big Joe's. [Docpool and Heise Online— Thanks Wayne]