Upon further reflection I think that sort of thing might start getting us into trouble. After all, if the bank still has the bitcoins, and if they figure a certain percentage of the bitbucks they issue will be out of their hands at any given moment, they can start doing things like:
1) Using the bitcoins behind the "missing percentage" to speculate. When they lose the bitcoins they will effectively be inflating the bitbucks economy.
2) Printing more bitbucks than they have bitcoins to cover. Let's say the bank is short some money and needs to pay off a debt *now.* Why not print off some bitbucks to represent that "missing percentage?" After all, it's not like there's ever going to be a run on the bank such that they'll have to actually account for that missing percentage.
By creating a physical currency issued by a single entity we will have re-created the Fed and the fiat system we are desperately trying to escape. Let's worry about the local stores that don't accept bitcoins before we worry about the villages that don't have access to the bitcoin network. If we need a physical representation of value, we may as well use one of the established fiat currencies, or else numismatics. Both of these currency classes can be bought with bitcoins and can be used to represent bitcoins physically.
If the time comes when the isolated African village *is* a worry for us, then let one of us who were here in the beginning bring the network to *them.* As society struggles on and the standard of living rises globally, the Internet will become almost as ubiquitous as gasoline or plastics.
I agree with what you're saying but I think it's almost inevitable they're going to do that. You don't need to give them permission.
It would be just how it is now. Bank has 1000 of your BTC in it and a guy comes in for a 100btc loan they'd give him 100 of yours. Now if you go in the next day and want your 1000btc all at once you've got a problem. Obviously on a larger scale more people etc. Also there probably wouldn't be any regulation / reserve rate so who knows maybe they take your 1000 and feel like loaning 50,000 out. It could be worse than the existing system in some ways. Also you know the average person won't understand. They'll see it as "I bought 10k btc and lost it all when it was in the bank, it's not safe".
Maybe being pessimistic but oh well, I'm just looking at how the banks can use it to benefit because they will.