Also note that numerous jurisdictions (see http://en.wikipedia.org/wiki/Legal_tender) will be excluded from the benefits of Bitcoin should it be called a currency (and thus be a foreign currency as opposed to the national currency, and thus not legal tender currency for payment purposes).  If Bitcoin is officially viewed as a commodity - it may be bartered with, in these (and all other) jurisditions and thus will have universal use.  The fact of calling Bitcoin a currency and not a commodity, may have a hindrance on international use (some jurisdictions may forbid or restrict PAYMENT, but not BARTER, made other than by legal tender) when Bitcoin establishes itself in the mainstream market.  For an interesting parallel consider the Islamic gold Shariah coin (with intrinsic metal commodity value, see http://www.islamicmint.com/news_articles/articles/statement_castineria.html paragraph 7.) in comparison to Bitcoin (with its intrinsic mathematical solution's value).

More currency, barter, legal tender info (see http://en.wikipedia.org/wiki/Currency) describes how a Central Bank may have sole control over a nation's CURRENCY (as opposed to foreign currency that are sometimes specifically lawfully excluded as payment substitute for the national currency).  Central Banks generally does not have sole control over COMMODITIES.

Exchange control also has legal implications when dealing in foreign currency (currency other than the national currency) in some jurisdictions (see http://en.wikipedia.org/wiki/Foreign_exchange_controls).

When owning the keys to unlock a mathematical problem, it should constitute a store of value in the form of COMMODITY ownership of instant access to a mathematical sollution to a complicated problem.