The banking part of bitcoins sounds interesting but I am new to this so I can only speculate, sorry if any of this sounds really dumb but I am learning about this and its going to help to think this through...
It looks like there is no rule of law so perhaps its going to be very difficult to do something like loans. The bank right now shouldn't be much more than accepting deposits and charging a security fee to the depositor. People are scared anyway of something happening to their computer, like a virus or whatever, so perhaps there is a way to alleviate that fear. Good old fashioned bitcoin safe deposit box.
Deposit security box is the first thing a bank would do imho, partly to establish trust and confidence in the bank (obviously being a registered business is required but until we have outside auditors of the banks, they have to earn their trust with potential customers.
I do think loans are viable just different from conventional banks. Much closer to the old traditional loan system,
I as the banker have N deposits of bitcoins (my load reserve)
U wants of loan of M bitcoins (M <= N)
U have to provide I with reason to I to loan you the cash, currently that would likely by the existing otp trust system.
If I think your trust worthy I calculate a interest rate on that risk, I loan you that money and you pay a portion of the loan + interest each month.
U default, I did my risk calculation wrong and take the lose.
U are a good customer, U get the loan, I earn interest and your risk ratio (and therefore interest) get better.