I like the idea so I'd like to share my thought processes as I used it.

Firstly, I had a basic idea of what it probably was having heard about the hack involving file hashes a while back.

While it gets permissions for my entire Dropbox I was aware it only interacted with my Public folder. That's fine.

After signing up it wasn't obvious what to do next, even with the random link. I searched for a file that's in a folder with no luck. My first random file is one of my own. through that trial and error I figured out it only interacts with the top-level folder.

Personally, I organize my public folder. In fact, I have a "persistent" folder that I use to link to, to imply the links are largely non-transient. I'd love to be able to index folders of my choosing.

If you redirected to a page to control that it would be immediately obvious what's shared and what's not.

EDIT: As an aside, I found some pretty neat files I'd forgotten about!