If you move internally within a country, sure. But when you actually move country, you'll need to get a new sim (or be charged roaming fees).

I live in Europe, and I've had 4 different phone numbers in the past 3 years.

Not everyone lives in the US. Here's how this affects me:

* If I lose my phone, I've permanently lost my number. * Long-distance calls are a lot more expensive (about 5-10x as much). * Switch companies? Number lost again.

I've had about 5-6 mobile numbers since during the last decade.

Over here (Germany) it commonly costs 30 bucks to transfer a phone number to another provider, at least if you are on cheap plans.

Changing counties comes to mind.

I went to school and got a new number because a lot of my friends didn't have free province-wide calling and I'm about to move from Canada to Europe. So for me this is a particular concern at the moment.