I've just checked the code. It indeed deletes the file once a download has been completely consumed, so it can't really replace other file-sharing services. BUT I wonder how does it deal with race conditions ? My guess is that if many people start a download at the same time, they'll all be able to complete it before the file goes away. At least that's how I'd see it working with S3 or local storage.

You could abuse it by sending the same file many times in order to create lots of download links; but there's little to gain in bandwidth savings: you might as well run your own server. The only advantage I'd see is hiding your IP address, but then you could also run a tor hidden service. The other would be bandwidth amplification by synchronizing all the clients (for big files).