I haven't bothered to test the API, but you've effectively allowed a fully-open upload API? Who's paying the storage costs, and how do you prevent abuse?
(Obviously I'm taking this more seriously than it's probably meant to)
I used to host 1TB on a cheap $1 VPS, it's quite easy if you just want to store stuff. The trick is to just connect to a networked drive at your home on the back-end. The VPS drive just acts as a buffer for the network. If low(-ish) bandwidth is acceptable, you can offer downloading too.
AceJohnny2 · · focus · HN ↗
(Obviously I'm taking this more seriously than it's probably meant to)
bArray · · focus · HN ↗
morgoo · · focus · HN ↗
layer8 · · focus · HN ↗