Spymarks just seem like another word for https://en.wikipedia.org/wiki/Steganography. On that note, one way we can prevent it is to assert that all our content is byte-for-byte identical with the last known trusted stage of what we have produced (for example: a camera we are certain does not watermark, an image editor we are certain doesn't watermark, an image compressor we are certain can't watermark, etc). One vector that I am particularly concerned about is social media. Most images and videos uploaded to most social media is re-compressed by the target platform. This is a door to tracking that is far too easy for social media platforms to open. They might rationalize it (if discovered/announced) by saying that our memes won't be reposted, images or work stolen, etc... but honestly I'd rather my work be stolen than tracking information inserted in there. Oh, we also have stuff which is way more secure, like time-stamped cryptographic signatures.

Spymarks an application of steganography, not a different name for it.

> On that note, one way we can prevent it is to assert that all our content is byte-for-byte identical with the last known trusted stage of what we have produced

That doesn't help with things like the typical use of SynthID where the spymarking is done by the same process generating the content, so there is never a clean comparator. (It also wouldn't be useful anytime it is inplemented as part of a transformation—compression, etc. —step, for the same reason.)

> Spymarks just seem like another word for https://en.wikipedia.org/…

Stop using links instead of words. Your comment is literally unreadable without going on to other websites.