aaaaaand right here. This is the point where the Ignore button comes into play.  You want to just create currency whenever someone decides they want to be part of the economy? Do you have any idea what that does to the economy? Go read up on Zimbabwe. A prime example of a country trying to money-print its troubles away. The Soviet Union, same thing. They kept printing rubles after rubles after rubles, till people were wheeling carts full of bills to the store to buy a loaf of bread. The 'create as needed' method has been proven to NOT WORK. Currency has to be backed by SOMETHING. With fiat, it's backed by governments, by reserves of precious commodities in vaults somewhere, etc. With bitcoin, it's backed by the network, the blockchain, the work that the entire bitcoin using community contributes to the health and promotion of the bitcoin economy. Every time I send 0.10 bitcoins to bitmillions.com, i attach a miner's fee (generally 0.005 for small stuff, 0.01-0.05 for bigger more important transactions), contributing to the network and to the blockchain, keeping the wheels of cryptoindustry greased.

That's what backs bitcoin. The common effort of every bitcoin user to sustain and nourish the blockchain.