...physical paper currency is actually constantly in short supply on the streets.
I went to Argentina a few times in the last years, and I found this particular fact rather astonishing. It was a real struggle to pay for anything because people often don't have change. So you have to be careful to break your bills in larger stores so that you later can afford to pay for the taxi home.
One more advantage of BitCoin. You will be able to pay for something in 0.05491 BTC and get exact change every time. (This is not quite the case yet as to reduce spam the client restricts transactions below 0.01 BTC.)
Businesses need to handle payments, pay suppliers, produce accounts and pay taxes. If their income is in bitcoins but their costs are in dollars, they need to transact between the two.
Indeed. I wrote up a doomsday scenario based, in part, on this idea (perhaps with a touch too much sensationalism in my tone):
https://bitcointalksearch.org/topic/how-a-social-attack-could-defeat-a-prosperous-bitcoin-network-6007 In the scenario a government co-opts the BitCoin infrastructure by mandating their own technology at points of sale.
It will be quite interesting to see how the network adapts to the first legal and social attacks upon it. I believe the result will be very much controlled by the effectiveness of the propaganda that will go with it. BitCoin is, unfortunately, rather easy to paint in dark colours for a crafty state. Add to it that the initial supporters could be seen in the public eye as 'just a bunch of anarchists'.
The one thing that stood in BitTorrent's favour was that file copying was widespread and well liked by the people before the media industry turned the spotlight of the law against it. Maybe BitCoin too could establish a wide and well liked ecosystem before it comes into the crosshairs.