Argh - this is a really good point.

I'm from the UK, so I often forget that: a) cell phones have area codes (unlike the UK), b) area codes do not change when cell phones move, and c) there's no way to tell a cell number from a land line number (again, unlike the UK).

Put those three factors together and you're right - the tool becomes far less useful for cell phone numbers.

I'll do a bit more investigation and see if there's a way to improve this situation. Thanks for the input!