Deflation is not a threat to an economy, and is not destructive in the same way that inflation is. Think about it this way, what is the harm to the economy if the consumer can buy milk for less than yesterday? And do you really buy the talk that the increasing value of a currency will lead to hoarding? If so, why doesn't it lead to hoarding now?
Spectators do all the working out for you. The price of bitcoin will have the deflating price
factored in at any one point. So people will trade bitcoin knowing that they are paying a higher price than the 'real price without expected deflation'.
The only thing to keep in mind is that the price of bitcoin will be directly related to the size of the bitcoin economy. So, just buying bitcoins and hording them, is directly equivalent to investing in the entire economy that uses bitcoin.