What happens to the telephone numbers that were ported if a VOIP
> provider goes out of business?
It depends. If another entity takes up that business it goes to them. If the business goes belly up and goes out of business entirely the number goes back to the original entity that was assigned that NPA/NXX-X. That's what happens when you port a cellphone number from one carrier to another. If service is disconnected the number goes back to the original party that was assigned that prefix (and thousands block if applicable.)
[TELECOM Digest Editor's Note: Except, when Prairie Stream went out of business (the owner had been and still is operating Terra World, the ISP here in town) some of us were afraid what you said would happen; that we would be 'migrated' back to Southwestern Bell (from whence we all had started, with our 620-331 numbers). Sage Telecom did not 'take over' Prairie Stream, Prairie Stream simply folded up. But many/most of us got a letter from Prairie Stream saying that company was recommending 'Sage' as a replacement, and that if we did not choose a replacement within 30 days, _then_ we would be automatically shunted over to AT&T (which was about to be taken over by SBC). Sage has worked out quite well for me. Any of you currently in SBC 'territory' who want to try out Sage (for about half the price of the 'new' AT&T) are welcome to test it out. If you will write _personally_ to me at my snipped-for-privacy@cableone.net address, I will tell you a number you can use to get me a $20-25 dollar credit on _my_ service in exchange for the referral. PAT]