[lsb]

No cellphones are allowed in top secret military locations in the US, because all can be remotely signalled to start recording audio. We know they'll turn a phone into a bug if they need to, so it's foolish to assume they wouldn't be able to get the real PIN.

[schiffern]

Do you have any evidence that indicates that this is the reason?

A much more likely explanation for the policy involves abuse by the user, either intentionally or unintentionally. Cameras and USB sticks are similarly restricted.

[pavel_lishin]

Yeah, I'm sure that the Princeton, TX police department has access to CIA-level technology, and will use it to prove that I was texting while driving.