Do you think BitCoins are being spent or are the vast majority of them being hoarded?
Neither. Most are purchased and saved. They are being saved to pay for future consumption. Or as a simply speculative buy.
That is not hoarding.
That also isn't necessarily a problem.
If bitcoins were not divisible, and there were only 11 million that could exist, then you'ld have a problem.
But instead of paying 1.0 BTC for a quick meal I now pay 0.1 BTC for it, the higher valuation doesn't limit me from being able to use them for my spending.
Because I can acquire more coins easily (with a bank transfer, sent to an exchange, for the cost of $0.25 per transaction using Dwolla, then 0.6% at my exchange) I'm not worried about using my coins for my spending.
But volatility is not good for a currency, so where a problem is introduced is when the exchange rate stops rising and those speculating on bitcoins start to dump. Each sell puts downward pressure on the exchange rate which incents others to sell.
So that's why bitcoins need to circulate as part of commerce using the coins as a currency rather than just seeing Bitcoin used as a trading vehicle for speculators.