The question is what constitutes money? A dollar bill is nothing but a piece of fabric backed by the "full faith and credit of the United States Government". Unlike US dollars Bitcoin is not running on a fractional reserve. You know what you get, and it has an intrinsic value given to it by its users.

Best comparison I can give is gold. It has no real value, but it's a scarcity with real life application, so we grant it a specific value. In my opinion, Bitcoin is superior to gold, given it's so easy to move, divide and trade. So perhaps we should call Bitcoins digital gold.