I've tested the friendly captcha demo and it is indeed way more fun and easier than the model we have now on plebbit.
I have a 12 year old 4 core thinkpad. It takes around 10 second to verify you are "human", although you cannot be human with POW captchas indeed. As with traditionnal captchas which can be solved with machine learning. But posting a vast amount of bot posts with POW captchas would take a vast amount of CPU power and electricity consumption.
Obviously that defeat the purpose of decentralization. But the plebbit team officially said that in the future it will be possible to create our own subpletbbit easily, directly from the browser, without having to install anything.
I just talked to him. He said he can associated the subplebbit-address record to someone willing to host the sub as he can't do much right now as he's very busy