OP doesn't understand how Fractional Reserve operates and I don't know if other posters here do either. It doesn't mean they only have to keep some of their deposits on reserve - it means they only have to keep a fraction of their loans on reserve.
If they have 1 million in deposits then they keep that as the fraction of how much they can loan out. They can typically loan out 10 x 1 million = 10 million. That other 9 million they "create" as debt. This is where the real profit power if. They can make interest on about 10 x what they have had on deposit.
When you give them your money they turn around and loan out more than you gave them and make interest on all of it.
I knew that already; I was just simplifying for expository purposes. Anyway, it amounts to the same thing, since if 90% of a deposit gets loaned out and re-deposited at another bank, then 90% of
that gets loaned out and re-deposited, and so forth, the sum of that infinite series amounts to multiplying the total money supply by a factor of 10 (just not necessarily all within one bank).
(Proof:
http://www.wolframalpha.com/input/?i=sum+from+n%3D0+to+infinity+of+b*%281+-+%281%2Fm%29%29^n . Here, b=base deposit amount, m=money supply multiplier factor. The corresponding fractional reserve requirement is then f=1/m. If m=10, f = 1/10 = 10%.)
Since they can create NEW money they can loan more than on reserve. With bit coins they cannot create new money and that is the SIGNIFICANT difference between the two. They can hold some deposits and loan out some but they will never be able to leverage YOUR money into BIGGER PROFITS.
That's not true. If the bank already has an accounting system set up for tracking Bitcoin-denominated deposit accounts, those accounts themselves are just ordinary numbers in a computer. So, if I deposit 1M BTCs, and there is only a 10% reserve requirement, there is NOTHING TO PREVENT THE BANK from simply creating a 10M BTC loan account
out of thin air (since it's just a new table entry in their database), and crediting that account with 10M BTC. This is how it's done!
If all that the typical customer does with their loan account is use it to write checks to other banking customers (as is usually done with USD-denominated loan accounts today), the banking system never ever has to come up with the "base" BTCs that are supposedly (but not really) backing all those account balances. The bank is then counting on the fact that it is very unlikely that their many different loan recipients and depositors will withdraw more than 10% their entire account balances in "cash" (actual BTC) form at any given time. The rest is withdrawn and transacted in the form of checks, or notes issued by the bank (cashier's checks).
This would be no different from the situation today, with the base currency of physical coins and bills. If all of a bank's loan account holders simultaneously demanded a withdrawal of their loan amounts in physical currency, the bank would probably not actually have that much physical cash on hand (since only 10% of that amount was deposited), and there would be an uncomfortable delay while it procured them through inter-bank loans and so forth. And if every customer in the whole banking system tried to withdraw all of their balances in cash simultaneously, it would be far more than there is physical currency in existence, the whole system would collapse.