Blockstack engineer here. The user pays for their storage -- you would supply your own space on a storage provider of your choice (be it a cloud storage provid

Blockstack engineer here. The user pays for their storage -- you would supply your own space on a storage provider of your choice (be it a cloud storage provider, your server, a BitTorrent swarm, etc.), and use it as a back-end to your Gaia hub. The Gaia hub can be run anywhere you want -- on a server, in a service worker in your browser, etc. It's only on the write path, so availability isn't too big of a concern as long as your storage provider handles the read path (which cloud storage does).