Correction... no. They don't need DB to download a file.

Sharing a read-only link instead

You can also link to files and folders in your Dropbox with a simple click. Friends and colleagues who click the link get a preview of the file in their browser with an option to download it - even if they don't have a Dropbox of their own. To see links in action, head over to this features page or learn how to make a link here.

But they can't upload.

A society grows great when old men plant trees whose shade they know they shall never sit in.