The banks are companies with the same rules like every other for profit enterprise.
They have owners, and the efficiency of a bank is depending on its capability to evaluate the risk of loans.
Means if there is no transparency / institutions etc. then the spread between borrowing ( deposits) and loans will be huge.
So what happen back in 2008 when the tax payers have to shell out TRILLIONS of dollars to bail out those "too big to fail" banks?