That said, I have been thinking that hoarding is a big problem. But, have you heard about the event that occurred on April 4, 2011? Supposedly 30,000 BTC were sold over a short period of time. Considering that the supply of BTC was just over 5 million, this is an extreme amount. Indeed, a transaction of this size did have some control over the market - we saw the USD/BTC drop considerably. However, soon after the ratio adjusted back to its original level. This indicates resilience in BTC itself and maturity in the BTC community. For this reason I'm encouraged that hoarding isn't the biggest problem that BTC faces.
I think the extreme price volatility is going to prevent hoarding, people who loaded up on bitcoins at $5 or less are going to be perfectly willing to unload them at current prices and take their profits. If the bitcoin price stabilizes vrs the dollar, we might have Gresham's law kick in tho, which could encourage hoarding.
Gresham's Law, "Bad money drives out good", just means that if you have two currencies in your pocket, one you trust, and one you trust less, when you buy something, you'll prefer to dump off your less trusted money and keep your bitcoins, or silver, or whatever it is that you have the most faith in for future use.