@etotheipi
The subject has been beaten to death for a century by various economic schools, and the general consensus of most economists, supported by empirical data, is that deflationary expectations destroy trade, reduce economic activity and makes everybody a bit poorer, save for those who hold the most money.
A rational agent holding Bitcoins will understand their risky nature so it's likely he will diversify to control risk - not dump all his savings into Bitcoin. He might hold one third of his money in a mutual fund, one third in cash and one third in Bitcoins. Of these assets, Bitcoins is the most risky, but it also has the largest potential upside.
Ok, if this rational agent is faced with a buying decision regarding a new iPad, what currency is he likely to use, Bitcoin or cash ? Two basic scenarios:
- as long as bitcoins are rising, it's irrational to spend them; it's like killing your best cow - it's much more profitable to ride the bull market
- if bitcoins have stagnated since the user has added them to his portofolio, it's irrational to spend them since he took all the risk but has none of the expected upside
Faced with this decision the rational agent will chose to pay with cash. He will treat Bitcoin as a long term investment, and only spend them if:
- he wants to balance his portfolio after a bitcoin rally and mark his profits
- he wants to liquidate his bitcoin portfolio for whatever reason
Both these events are rare, so the velocity of bitcoins will be extremely low, and will mostly be related to cash <-> bitcoin exchanges. Thus Bitcoin's potential as a trade facilitator will not be fulfilled. On the other hand, an slightly inflationary cryptocurrency which has similar risks but no potential upside will be spend by it's owners like there's no tomorrow. Nobody will treat it as an investment since it's guaranteed to loose some value in a year or two - the hot potato game. The much higher velocity means higher GDP and strong merchant revenue in this alternate cryptocurrency.
Yes, given an unlimited supply of two currencies of unequal merit, it totally makes sense to unload the loser. Congratulations, you've found a really convoluted way to restate
Gresham's Law.
In reality, the rational agent will run out of dollars eventually, or run out of people willing to accept them.