In the current system, you can lend out like 10x your own reserves.  If there's a run on your bank, the central bank will print more dollars and keep you afloat.  That can't happen in bitcoins, because there's no printing new bitcoins (above what mining does).

So, if banks lend out more than they have, they will go bust in periodic bank runs.

This means *far less* lending, because depositors to the bank are far less secure.  Thus, they will demand higher interest rates.  (Yes, even though the currency is deflationary, interest rates would be very high because of this risk.)  So, there wouldn't be so much easy credit.  The housing crisis probably never would have happened, for instance.  If something like that did happen, the fed wouldn't have increased the money supply by trillions, which is why you get .5% on a savings account right now: you are competing as a lender with the Fed, who is giving select big banks basically free money.

But there will always be risk-taking in any economy, always bubbles, always human irrationality.  No currency can stop that.  It's driven by human psychology and the dynamics of exchange.