Brian Armstrong on Bitcoin:
An open payment network is a game changer…so why hadn’t an open payment network existed previously? Until recently, many people thought it wasn’t possible to build a payment system on an open network. The core issue was around preventing duplicate spending without using a central company to verify each transaction. Nothing prevents you from sending duplicate emails multiple times, for example, if you wanted to do this.
This problem (the “double spending” problem) is what Bitcoin solves, and in this sense it truly was a technological breakthrough or invention (one that I think will be viewed as very important historically). If you’re someone in the business of verifying transactions on a proprietary network, the invention of Bitcoin cannot be safely ignored. It will change or disrupt the providers of most proprietary payment networks in the coming years.