AFAIK, fractional reserve is the bete noir for many believers in bitcoin.
Then they're hosed, because as soon as somebody somewhere makes a loan using bitcoin, then bitcoin becomes a fractional reserve currency.
Edit: It seems that some cryptocurrency folks have confused "fractional reserve" with "fiat". Those are two very different monetary concepts.
No, there is the other option called full reserve banking.
It's not like cryptocurrencies can change human nature.
if i borrowed 1 bitcoin from you, and then i default, then how are you going to pay back that bitcoin to whoever deposited it?
If you want a lockbox, get a lockbox. If you want a deposit account, you're storing and retrieving fully fungible and interchangeable entities.