Protect your Location Information by using UMTS - Surf Sticks

Did you ever wonder how some websites know your location ? This is a very good example of a service doing this: Locate your IP

Basically the principle is based on using your IP address and comparing it to other addresses in your area while relying on some assumptions about your Internet providers IP address allocation. Read some details in: Accuracy of Geolocation

A very easy way of protection is to use an UMTS-Surf Stick. While the mobile operator might be able to locate you even under this circumstances, your IP address will very likely not reveal your location to any Internet service anymore.

Not sure if this is of any use to anybody. Put I though this to be interesting anyway. Is there any basic flaw in this reasoning ?
OJ