Easy test: Do you get any bills from any companies which are denominated in Oz of gold? No.

Are there some coins which are plated in, or made FROM gold? Yes.

Both are commodities IMHO. The volatility problem of BitCoin is a serious one.. until the market calms down to the point where coins have a relatively fixed value or appreciate at a relatively sane rate it is completely impractical to use this as a currency, much better as a medium of exchange

As for the practical applications for this kind of a digital commodity.. Vice has, and always will be the best early adopter: Drugs, Guns, Porn, Gambling. Once these guys dive in with both feet it will be fantastic and could morph into a real currency.