I wrote about seasteading years before it had that name (I think), and I've long been an enthusiast of space exploration. But it seems to me Peter Thiel offers a rather quixotic and counterproductive idea that libertarians should be throwing their energies into building new societies on the oceans or in space (or in cyberspace, though that's less of an all-or-nothing proposition), in lieu of the supposedly hopeless task of making existing societies more libertarian.
Brian Doherty expresses some skepticism as well. Incidentally, I once made Patri Friedman "want to scream" at my supposed obtuseness in an earlier discussion on some similar points. But I think part of the disconnect is that libertarians entertaining such ideas tend to have a more principled/extreme (take your pick) view of what constitutes a free society than I do.
UPDATE: At the risk of stating the obvious, I'd add that it's going to be a long time before anybody is going to be able to live in space, or in any desirable way on an ocean platform, without extensive support facilities on terra firma, including, not least, a bank account.
UPDATE 4-21: Actually, it turns out the market will solve these problems.