Could a national currency integrate into the block-chain if they wanted to? For example, Canada could issue 'authorized' bitcoins, meaning the coin had to originate from an official source. And if the coin originated from an 'authorized' source, the value could be pegged at a certain price -- backed by the gov't? This way the currency could adopt the flexibility and convenience of bitcoin -- while retaining the ability to issue new currency.
Edit -- to clarify, a mint could purchase one coin, and peg the value of .00000001 of that coin to $1. Only transactions originating from this official coin would be treated as official currency.
Bitcoins don't have IDs - it's only amounts being transferred between addresses. If I have 5BTC in my wallet, I have no way to differentiate between let's say the 0.01 "canadian" and the 4.99 ordinary BTC. i could not specify which ones to send in a transaction.
That said, if MintCoin gains momentum I'm sure there will be plenty of MC-BTC exchanges popping up.
That is wrong. Maybe the current client implementation cannot do this, but the open block chain allows one to exactly see where a coin originated (i.e. whether is is Canadian or not). Alternative implementations could then be told to specifically spend the Canadian or regular coins.
I don't think it makes sense to use block chain technology for backed currencies; if you're going to have a central mint anyway you might as well use a Chaum-style system like Lucre or Open-Transactions.