I mean I love the concept. However something makes me suspect none of these will be the completely-walkable, full of art, no-pollution, no plastic, utopia city I'm thinking of.
I assure you that there is plenty of potential harm in trying to make extra-legal mass scale social programs.
The most obvious one to me (based on every large social institution's past history), is how these places will handle sex crimes. There will be a poorly managed or entirely preventable sex crime scandal at one of these places. I would be willing to bet on it.
There are plenty of other things that I foresee failing, but this just looks like seasteading 2.0 to me. There is a reason that libertarians on a cruise ship failed, and given the involvement of some of the same characters, I would also be willing to bet that these concepts will fail in the same way.
But no harm in them trying their idea...