A fascinating read for anyone that wants to understand how little anonymity you have when using a mobile phone in the United States.
Some choice quotes:
... the FBI can trace any mobile phone number to an exact location on US territory. This method is called "triangular lookup" or "triangular trace", or just "triangulation".
This way of tracing is very reliable and is used a lot by the FBI
In other words, the second you turn on your phone in the US, they can track you easily and quickly. Combine that with records of internet use and the fact that most servers are easily hackable by those with a little bit knowledge, and you can see how quickly and easily the authorities can track down anyone of interest.
Anyone that believes that they are anonymous online should read about how the FBI caught up with the Silk Road owner. Fascinating stuff, and shows how easy it is to get caught over there for online crime.