Had the same question. I already put a lot of posts in seemingly cool but empty geohashes (#1971, #1984, #888, #HH, #420, … ) but none of them seems persisted and also: how/why would I own them because of that? As far as I understand geohashes cannot be owned in any enforceable way. They can only be used. And that requires constant effort to provide useful content plus probably somehow keep spam at bay. Maybe that is what he means?