> Could a NFC enabled Smartphone act as a payment terminal?

I don't know if there's a technical reason why not, but the security requirements for these devices are fairly stringent and getting a piece of software, running on a relatively open system with other apps from unknown sources all over it, well the certification folks would probably take a hell of a lot of convincing.

Not saying it can;t be done, but I don't think I'd like to be on that project.