Hoarding, while unlikely due to the reasons given, can occur - look at the bank runs and liquidity crisis of the Great Depression while the U.S. was on a gold standard. This is a problem with any sort of fixed supply currency, i.e. gold and possibly bitcoin.
Pre- civil war, U.S. banks were (somewhat) free to issue their own private bank notes e.g. dollar bills (I say "somewhat" because there were still government restrictions requiring banks hold a certain types of bonds - usually government bonds of course - as collateral). The banks backed these notes with gold, but it was still fractional reserve banking in that the banks didn't keep enough gold on hand to redeem all of their outstanding notes at once. When there were bank runs, banks could print more of their private bank notes to meet the demand for currency, just as a bakery would make more bread if the price of bread went up due to increased demand. Demanding gold was often impractical given the difficulty of using it for daily purposes.
Scottish free banks, interestingly, included a redemption clause on their bank notes allowing the banks to refuse to exchange the notes for a certain period of time. However, if they did refuse, they had to pay a penalty to the bearer. This helped to prevent bank runs for two reasons. First, people knew if there was an attempted run on their bank, the bank would refuse gold redemption, hence making it useless to run on the bank in the first place. Second, if there was a run, banks would block redemption thereby giving them enough time to liquidate assets.
Overall, the flexibility under free banking to issue private bank notes (and destroy them) kept the money supply flexible and therefore helped to prevent erratic changes in prices. Money is a good just as bread, cars, or oil. If you fixed the supply of these goods, prices would likely become more volatile (the history of OPEC provides some evidence of this).
I think it would be interesting to explore the idea of bitcoin banks that use bitcoins as "gold", and then issue "bitnotes" that are backed by bitcoins on a fractional reserve basis. Of course, people would still be free to keep their bitcoins in their digital pocket, or even use fully-reserved banks.
Yep. I have been thinking about how to mix the ideas of free banking with bitcoins. One way could be through gold and silver merchants acting as liquidity stabilizers, but still it does not have the flexibility of fractional reserve banking. I am curious about how the bitcoin banking system will develop.
Btw, at the begginning of the Great Depression the Federal Reserve tighten the money supply so it can not all be attributed to people panicking and demanding cash. It is true that after a short initial period of tightening the Federal Reserve started loosing up like crazy. But the problem is that during the crash of a bubble people will panick and save more cash. Its an unavoidable consequence of the boom and bust produced by central banks. Even when central banks try to avoid this effect they can not, because when the bubble crashes the banking system becomes broke and freezes the credit channels, making the efforts of central banking almost useless (as we are seeing during this crisis). This is why keynesians always demand government spending through monetized debt, because its the only way to save the banks by avoiding any kind of deflation. The problem is that these mesures produce distortions on the capital structure prolonging the crisis, perpetuate the central banking system, concentrate the banking system in a few hands and make the middle class and the poor even poorer. Its an unavoidable cycle if you have a central bank.
PS: Count me in the camp of the one that spends when bitcoin goes up in price. To the ones that keep saving their bitcoins when price goes up: you should think that after the price goes up, it usually corrects down. At some point bitcoin is going to suffer a major downward correction, so you should think about starting to spend your bitcoins.