Like Hawker said, it's really complicated to set up a regular loan process much less one around Bitcoin. For a Bitcoin banking industry to work, you'd need other supporting industries around it. For example, how would you handle someone who refuses to pay back their loan? You can't really send men with guns after them to put them in a cage and you can't contract with a regular private collection firm to do recovery without devaluing the transaction and losing money.
At the very least you'd need 1) a contract that specifies how much is to be repaid and when. 2) And independent arbitration firm to handle disputes 3) A collection firm the could recover your assets in case the borrower doesn't pay.
I'm not saying this couldn't work. The first two items are easy. The third could be handled by attaching the recovery process to the collection of fiat money. If the borrower didn't pay back the bitcoins, you took some of their cash if arbitration sided with you.
It's a complex thing but pretty doable if the market were to cooperate to create/extend the needed services.
Rage
I agree with all the 3 points but i think point number 3 could be executed by another company. And yes. Suddenly if someone steals you, you will have to use the violence to defend your self, so if you lend me some money and i don't repay you... then i think it's not inmoral for you to take whatever i promised to give you in compensation (in example my car).
I think there are minor issues that must be thinked but, in general this economy wont start seriously without a system to invest in new projects.