Google Voice - what is it?

What is Google Voice (nee Grand central)? It is clear that one number for life, and redirection from this number anywhere, on landline, mobile or in SIP. Plyus google sweets, such as voice recognition in voice mail. This is all a set of functions of a standard virtual PBX, nothing new here.
What's new is that Google is going to distribute numbers for free in all US states! The information is now very scarce, in connection with which I would like to discuss some things.

1. How are these free numbers? Where will they take them in such numbers? With a Google audience, it's millions of numbers.
2. How is this free call forwarding? Forwarding to a mobile, in essence, means an outgoing call to a mobile, which is charged. Who will pay?
3. How will the outgoing (redirected) calls to the PSTN or to the mobile be organized technically? Will they install their equipment throughout the country? With all due respect to Grand Central, the scale of Google is incomparable.
4. And if I left to travel with my mobile, will they build their VoIP gateways across the country and drive long-distance traffic over the Internet or will they use some cheapvoip?
5. What will they have inside? Sip? Why then are not supported SIP devices except Gizmo.
6. What will happen to businesses selling DID numbers? Will they die?
7. How many channels will google number?
8. Will they start stamping IVR type functions, call queues, waiting time messages killing PBX business?

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