(1) is a definite failure point, and (4) is going to be done for free by hobbyists. The best-case scenario is that the proposal helps keep honest people honest,

(1) is a definite failure point, and (4) is going to be done for free by hobbyists. The best-case scenario is that the proposal helps keep honest people honest, reducing the number of malicious actors. The problem is that the malicious product is nearly infinitely scalable, enough so that I expect services to crop up whereby people use rooms full of trusted devices to attest to your favorite photo, for very low fees. If that's not the particular way this breaks then it's because somebody found something even more efficient or the demand isn't high enough to be worth circumventing (and in the latter case the proposal is also worthless).