Some guy in Texas was charged with running a bitcoin ponzi scheme. His defense was that Bitcoin is not a currency therefore, no ponzi scheme. Not so fast - according to the judge:
You can read the entire ruling here
It is clear that Bitcoin can be used as money. It can be used to purchase goods or services, and as Shavers stated, used to pay for individual living expenses. The only limitation of Bitcoin is that it is limited to those places that accept it as currency. However, it can also be exchanged for conventional currencies, such as the U.S. dollar, Euro, Yen, and Yuan. Therefore, Bitcoin is a currency or form of money, and investors wishing to invest in BTCST provided an investment of money.
You can read the entire ruling here