how about using a script that geocode's the person's IP when they sign up, and just publishes what country or geographic region they are from.
for example my IP geocodes to North America, then to USA, then to Michigan, then to Traverse City ... sometimes the geocode isn't that accurate or detailed, so sticking with Country or geographic region would still be great, giving us a clue as to where someone's located. As an example of accuracy, the geocode of Traverse City isn't accurate in my example, my IP may originate there, but I certainly dont, not even close.