@renardboySo like, from a chartalist perspective, currency has value because people are required to pay taxes in that currency — or else, straight to jail.
Ultimately, money gets its value from the barrel of a gun.
The evidence for this: central banks and commercial banks can create money simply by typing numbers into a computer — so there's clearly no relationship between amount of work performed and amount of money created.
Nor is there any direct relationship between scarcity and value, seeing as how no one wants to let me buy things with these jars of farts.
I can't pay my taxes with gold, or bitcoins, or jars of farts. Dollars, on the other hand? Yep, I need those to pay taxes.
And/or the shopkeeper needs dollars to pay taxes. So even if the shopkeeper accepts payment for things in bitcoins, they'll still need to sell those bitcoins to get dollars to pay their taxes.
This is why bitcoiners always doth protest too much, by saying stuff like "1BTC=1BTC" as if the dollar value doesn't matter to them, and pleading for things to be denominated in bitcoins.
But the actual fact is, nobody buys bitcoins to have bitcoins, and nobody wants to buy or sell goods denominated in bitcoins. They buy bitcoins hoping to sell the bitcoins at a later date for more dollars than they paid for them. Bitcoin, therefore, is a bubble and a scam. It's the dollars that have value as currency.
@mcc 
