This doesn't seem significantly better than just having the organization providing a video sign it as "authentically theirs", in cases where that's possible; if you mean some sort of thing where editing software and cameras will sign things as "not tampered with", then this is effectively a DRM system and subject to the excitingly wide range of issues affecting that. This would not work for many situations, particularly the ones SamBam describes (not least due to the anonymity thing), as it is unlikely that there will conveniently be someone there with chain-of-trust-capable recording equipment and software.