Well, I'm using different IPs than the "home" IP we used when we signed up. Any attempts to get into google voice for me, though, say that it is not allowed outside the USA.
Yep, so they just filter by whatever IP you are connecting from from outside the US and that's it. Countless websites and services have been doing that for a looong time - just as evil but should not have anything to do with cookies because then you should be able to sign in just fine on a different machine and use voice.
