I'm not a dropbox user, but I've always imagined you could simply mount your dropbox as a file system?! I'm surprised that that doesn't seem to be the case.
One big place the docs fall down is explaining how it talks to multiple dropbox accounts. Or how it authenticates to any account at all. I'm not nearly as interested in uploading to one dropbox account as 50, or 50K.
The usage case is probably something like an ebook delivery service where you release edition 3 of your "learn trendy language in a ridiculously short amount of time" so you run a script and all 100K previous buyers magically have ebook_version_3.pdf magically appear in their dropbox. There are ebook publishers doing this now. Like Pragmatic. I would imagine they have a tool vaguely like this in their backend system. Or teams of hundreds of bored interns doing it all by hand. Perhaps there's a completely different API for .com bulk uploading. Hopefully we never get Dropbox spam delivery.