A very old and evident observation.
Not exactly enlightening, but there you go.
Sounds pretty serious business to me.
This would affect any attempt at making something like this. I'm not sure that you can enforce the human/address connection in software.
It's a hard challenge, but not impossible. Online banking (mostly) works because it's possible.
I don't need to keep it a secret that I'm eating a burger, for example. It's pretty fun and liberating to have as few secrets as possible. Less things to worry about keeping secret, less work (and I'm lazy).
While that's true, a state has much more power in "assigning" value to currency. They have the power to levy taxes on all economic activity in their territory, and the power to demand payment of those taxes in the national currency.
If you have a job, do business, or make any other sort of profit in the U.S., you must pay taxes, and you must pay them in USD only - otherwise the state will throw you into jail. This means that there is always a demand for USD, no matter which other currency you use for transactions.