What is Google Voice?

What is Google Voice (nee Grand Central)? It is clear that one number for life, and forwarding from this number anywhere, to landlines, mobile or SIP. Google’s sweets, such as voice recognition in voice mail. This is all a set of functions of a standard virtual PBX, there is nothing new here.
New is that Google is going to give out numbers for free and in all states of the USA! The information is very scarce now, in connection with which I would like to discuss some things.

1. How is this free number? Where will they get them in such quantity? With a Google audience, it's millions of numbers.
2. How is a 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 outgoing (redirected) calls to PSTN or mobile phones be technically organized? Will they put their equipment nationwide? With all due respect to Grand Central, Google’s scale is not comparable.
4. And if I went to travel with my mobile, will they build their VoIP gateways all over the country and will drive long-distance traffic on the Internet or will they use some kind of cheapvoip?
5. What will they have inside? Sip? Why then SIP devices other than Gizmo are not supported.
6. What will happen to businesses selling DID numbers? Will they die?
7. How many channels will be on the Google number?
8. Won't they start stamping functions like IVR, call queues, timeout messages, killing the PBX business?

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