Theorycrafting: Idea(s) for decentralized social network

Has anyone built a social network on any blockchain? It seems like a nearly ideal foundation to use: no central servers needed (ezpz scaling), excellent privacy (right?)... the biggest hurdle I see is portability between different blockchains, which actually seems like an opportunity to promote/build an open standard.

My actual idea for a social network: they've all had gimmicks to help get them running. For LiveJournal and MySpace, the novelty of having one's own webpage was enough. For Facebook, it was the school exclusivity. For Instagram, it was the focus on photos; for Twitter, it was the limited length of posts.

My idea for a gimmick: posts can be viewed a limited number of times and/or they have GPS locations associated with them*.

Facebook was originally relatively inaccessible without "friends" who already had accounts; I would maintain a focus on that feature... and now I'm noticing that I'm making a wishlist of features for socializing via computer.

UX summary: create post, set limit to view count (up to 20? how to determine the maximum?), set viewers and/or repliers to whom the post is accessible, set location (or use device location*), and publish.

*... yeah, I know, security... I just think browsing works way better if it's more random instead of strictly filtering by idea/subject/topic/title/etc. (What if you want to browse for idea/subject/topic/title/etc.?) Giving posts location metadata (whether or not it's meaningfully linked to afk space) enables a more abstract, benign way of organizing them.

Profiles could be a thing, too. I have zero innovations in this area XD

Sent from my iPhone Typed on my mechanical keyboard.