Correct me if I'm wrong, but don't some bank services, like the infamous mybitcoin.com, offer an instant payment service for it's members? This actually increases the oppurtunity value of your BTC since there's no need to wait for block confirmations.
I'm not sure what all the services were that mybitcoin offered, but they definitely can't change the fundamental characteristics of bitcoin. There is no way they can guarantee instant transfers from external accounts without simultaneously losing the guarantee that your funds are actually 100% available at any moment. They can "guarantee" instant transfers internally from mybitcoin->mybitcoin, but these transactions are reversible, unlike real bitcoin transactions.