I would assume that's the only viable business model for this kind of thing.

Do phone numbers really cost anything in the US? Or is there an upper limit to the length of a phone number? Otherwise, they can just allocate a million which would be enough to have a grace period of at least a year until phone numbers would be reused.

All phone numbers in the US (actually, North America and some Caribbean islands) are the form AAA-XXX-YYYY, and there's a finite number of AAA (or area codes) that have been issued so far. And some types of numbers are not possible, mostly for historic reasons. I'm not sure how much a block of numbers actually cost in the US, but they're not free. I know a company I worked for tried hard to compress the range of numbers they had so they could give back part of an exchange to save money.

http://en.wikipedia.org/wiki/North_American_Numbering_Plan#N...

Perhaps they provide extensions for the numbers to avoid this issue?