alt Hacker NewsGhost keys will ultimately be just one of a menu of options for bootstrapping reputation in a decentralized reputation system. They have the advantage of simplicity, anonymity, and helping to fund the project, but as you correctly point out - they are centralized.
A cryptocurrency-based solution like you suggest will undoubtedly be one of a menu of reputation bootstrapping options that will develop over time.
Reputation systems have been a theoretical idea for a while, but we haven't come up with anything sybil-proof without centralized identity management. "we have a menu" sounds a lot like "we don't actually have any viable plan" in this case.
Don't get me wrong, this is awesome. I think it is built on a subtlety bad premise. I think it is time to start build organizational nomic games on this sort of contract system, literal organization governance, for systems like this to thrive.