This sounds like a great product, but what's it do that Dropbox doesn't? Sharing files was a massive pain in the ass a few years ago, but Dropbox makes it dead simple now.
Last time I checked there were two options for transferring large files on Dropbox. (1) if the recipient has dropbox as well you can just share the file privately. (2) If the recipient does not have dropbox, then the only way to share the file is to put it in a public folder where it will become publicly accessible to anyone.
It is obvious that this does not solve things for all situations. In my case I had to send a copy of our software build to a potential client. I did not want to make our software build public. And it would be certainly considered rude to ask a potential client to sign up for dropbox just so they can test our software.
I think most HN readers kind of assume that everyone has dropbox by now, but this is not something you can rely on once you get out of the US tech sphere.
So yes a service like this would be pretty useful.
From Drew's Dropbox YC application: "# What's new about what you're doing? * Most small teams..."
Also it's great how their desktop app acts more like an email-client for large files. It might not be as cool as having a shared folder in the cloud, but it seems like a superior path to adoption if the change to people's behavior builds on the way people do things today (attach files to emails).
Another quote from Drew's Dropbox YC application: "# What are people forced to do now because what you plan to make doesn't exist yet? * Email themselves attachments. Upload stuff to online storage sites or use online drives like Xdrive, which don't work on planes."