Partnering up with Moneybookers, Liberty Reserve, and paypal to provide instant transfers of USD to your exchange account.
While that is very, very cool and I look forward to seeing that being made available, I think casascius was referring to the method for someone who already has bitcoins to transact with someone else without waiting for confirmations.
If the API is kept generic enough, any trusted party can be substituted for MyBitcoin.
I've seen this discussed, but cannot find the thread. Here's the closest -- Mt. Gox describing an agreement between exchanges to act peer-to-peer. That would allow me to spend to your ewallet instantly because your ewallet provider trusts my ewallet provider.http://forum.bitcoin.org/index.php?topic=7212.0
We're really trying to make bitcoin be something it isn't though. Bitcoin wasn't meant to provide instant transactions, and moving us over to "centralized" ewallet systems to get that is not ideal.
If Open Transactions truly works the way fellowtraveler describes it, then with the audit protocol, that really is the right way to do this (see #4):