What's the long term value of paying for highly redundant, (yet highly gameable) custodial tracking of a piece of digital media when a dozen competing blockchains can be flooded by a hundred perfectly identical looking fakes made by altering a single bit in a single pixel, to generate a new hash and merkle root? Will enough people care that they don't have a signed original pepekitty by banksy when essentially perfect fake copies can still be made and distributed? Blockchain does nothing to solve this

OP said this could be a way to address fake news, and I agree, but there is a component missing.

What is needed is a system on a chip that immediately encrypts, signs and uploads any image (or video or audio) shot from the camera to a distributed public record, like a blockchain or IPFS. That gets you a creation timestamp and an unaltered source image that can be verified later if the author releases the decryption key.

Without having a SoC doing everything at once, any image that gets encrypted is already suspect. I’ll be surprised if devices like this don’t start appearing over the next few years, either for adoption by journalists or forced onto police. Apple is in a good position to do this with their devices, since their t2 chip is already managing authentication and the camera + microphone.

I think you're missing my point. The original concept framed by Kodak was protecting IP, so that freelance photographers or whomever (likely large corporations) don't have their pictures re-used. But I'm saying that blockchain watermarking could have greater immediate appeal to the public when it's reputations and lives on the line. So journalism organizations and media corporations end up buying watermark protected hardware to ensure the veracity of content.

But what value does "blockchain" add here? What is so special about photo watermarking that makes a traditional database unsuitable to the purpose?

If anything, the transaction rate limits of current blockchain technology seem like they'd be hugely limiting for this application...

I guess you could say that the fact it's using a block chain, any form of processing the transfer of ip/rights of the hash desired, can be out sourced. Bitpay, meta mask,. Etc

Side note I see no reason to use pow for this application, pos seams like a more appropriate security tradeoff