I'm not saying this will be the next Dropbox, but dismissing products so offhandedly because you underestimate the average user's aversion to "writing a few lines of Javascript" is silly.

This is nothing like dropbox. This is barely a hello world app on the Twilio platform. I have little doubt he could write a tutorial to walk people through it in an hour two two.

This would be a good analogy if you dropbox was literally just provisioning a user and setting an FTP password. And if it was, Dropbox would hit scaling problems on almost day one.

This won't hit scaling problems because it doesn't do anything... Twilio's API has built-in API calls for all this stuff and the webhooks can (and should) be hosted on AWS Lambda or Google Cloud Functions for pretty much free with automatic scaling.