I think many of us run our own NAS or document server or something... or even just an rsync and off-site system. But delivering this to users as a turn-key sol

I think many of us run our own NAS or document server or something... or even just an rsync and off-site system. But delivering this to users as a turn-key solution is a challenge. If your role is to just provide software that works together, there are some not-too-difficult solutions out there but still a lot of ways to mess up the replication or keep things from getting pwned. If your role is to provide availability and reliability, the economies of scale and totality of control that a centralized system provides just wins out over an indexing of the user's systems. EDIT: I missed that your question was specifically about browser access. tbh I think it makes the most sense to deliver the files directly by the server, with maybe some media controls for specific file types but even that is something the browser can basically take care of out-of-the-box.