Could you give an example?  I don't believe this is true.  Most currencies (gold, silver, etc.) naturally arose due to market forces, and new currencies (U.S. dollars) were based on these existing currencies and were forced into use by law.  Bitcoin is a rather unique case.

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.