Can be cheated or played, special HW requires central authority. - I am identified in mtgox through a yubikey (+ some personal data - see wikipedia link)
Requires a central authority to manufacturing yubikeys- I am identified in Bitcoin forum through my activity (+ some personal data - e-mail, ...)
can be played, and requires a central authority[/list]
bitcoin is designed to be DECENTRALIZED, it is a feature!
Therefor it does not need a single point of weekness. your plan is to introduce a SPOW into the bitcoin system, which is BAD. if we did that there would be no need for a blockchain at all, as the central authority could just validate every transaction, like creditcard companies does right now.