Lets say this...
TheSpanishGuy can you give me a loan of 1000BTC I will return you a 1200BTC for 1 year.
When the year end... how you will catch me to return your money?
1. my business can fail.
2. i can be a bad man that just not want to pay you.
3. many more options.
So how you as a bank is a save? How you will return your investment? A collection firm from US will go to Namibia ( for example ) to collect the loan?
Of course you understand that all this is a just example to explain you why I just not see how the system can work.
These are the problems that ordinary banks and businesses giving credit face as well.
There is a number of ways to reduce the risk of lending.
The risk of the borrower never repaying the money will always be present.
The interest rates paid by the borrower will reflect the likelyhood of a typical borrower taking the money and not returning it.
The bank, in order to try to make sure that the borrower will not take the money and run, will have to:
-Make the borrower sign a contract, that contains a clause that will make it unfavorable to break the contract.
-Make sure that the borrower is thorougly identified.
-Make sure that the borrower has a good reputation (ie. something to lose)
-Make sure that the borrower is within a jurisdiction that the lender is comfortable with, should it end up in arbitration or legal issues in general.
-Require the borrower to offer some sort of security. This can be anything from a car to a domain name as long as it can be legally secured by the lender in case the borrower defaults.