Hmmm. I wish I hadn't started thinking about that.

There's sort of a minimum match length too. Imagine the case where you have a friend with the number 321-214-0404, and then you try to text Twitter at 40404. Carrier numbers can get down to 4 or even 3(?) digits.

Sounds like that's a separate problem, though. I hope nobody adds '1' as a contact's phone number.