I was unaware you could share any folder/file before so I just played around with it. From your file manager, right click any dropbox file or folder and select 'Get Link'. The browser will open and send you to a page displaying all those files and folders. You can copy/paste that link to anyone.
Is the only difference that in the case of linking to a single file, rather than a full directory, the link clicker now sees a preview of the file (with a big Download button) instead of downloading it directly.
Isn't that actually an improvement, so the linker isn't just blindly trusting and downloading a file from some random link? That seems ripe for abuse, if users got used to that mindset.