“And it is out of any doubt that it would be stupid, at least at the moment, to make a contract for a DSL line in order to use it for VOIP.”
What about a ADSL line that cost $25 dollars a month, but you could save $250.00 a month on overseas calls.
You are kind of narow minded on some of your ideas.
Some scenarios that take the air out of your idea.
Not everyone get unlimited local calls.
Most Californians pay for each call, even locals ones.
Who will pay for few thousand call just to be a nice neighbor???
Someone calls and oreder 1 kilo of a white powder usinf your phone line. Police show up on your door saying that the call got traced to your phone line.
Someone make a terrorist threat, make purchases using stolen credit card, call 1900 porno lines, call the operator and ask for a person to person call to Timboucktu, etc.
How do you prevent it.
Hot spots that work for 500 meters.: I guess they will be unlicenced to be easily to instal.
I still have not seen a device that send signals without external antenas that have that range on unlicenced frequencies.
Try to install external antenas in most homes, on any civilized country.
Nice idea, lime comunism and other utopias.