3) What would happen if one attempts to send an amount of coins to a Bitcoin Address that nobody owns?
4) What would happen if one attempts to send an amount of coins to a Bitcoin Address that used to be owned, but has since been abandoned (recipient stopped running the program, or deleted their wallet)?
I guess the money will just be lost in that case.
Perhaps there should be a feature against this? For instance, if a transaction isn't accepted by the recipient for a long period of time (a month?), the transaction will be canceled and the coins returned to the one who sent them?