I don't think there's a trivial amount of computation people would want to perform that would cost too much for bots to advertise. I don't think people would be willing to wait 20 minutes on their phone to post a comment on a website. Assuming it's SHA256 like Bitcoin, from this video [1] a Samsung S22 Ultra does 400Kh/s. On a 6700 XT, the hashrate is 24 MH/s, that is like 50 times faster, or 24 seconds per post. If they use an ASIC it shoots up to the TH level. That's milliseconds. The service would need to be unusable on a phone unless people leased servers to validate their posts on, leading to costs for each post.
Proof of work also depends on capital, compute isn't free. In fact, it is already incredibly centralized in the Bitcoin blockchain because there's like 3 big players which have already attacked the Bitcoin Cash blockchain. The only reason these huge pools haven't attacked the Bitcoin blockchain is because they have a financial stake on the price being high, which is also the same incentive proof of stake depends on.
I'm gonna love trying to figure out what query gets the support chatbot to pair me with an actual human so that I can solve something that's off script
AI based SEO will be way worse, if Bing chat catches on then you'll be wishing to go back to the stuff that was written by humans with a vague understanding of how SEO works. SEO for AI LLMs is basically impossible to figure out as a human, since they are actually just complete nonsense, and the most optimal thing is to mine for phrases that will give you the answer, and OpenAI just sells access to the tools to test for that.
SEO for AI will be worse. Their output is a probabilistic distribution conditioned on the text is has read, so you can place text that heavily biases the output. Usually figuring out what this is can be kind of hard, but since OpenAI lets you query GPT-4 for credits, you can just mine what these special phrases are.
[1] https://youtu.be/iXMHKZGVZ0g