Dropbox Public Folder’s links and privacy

I think this is fine if you are only testing something for a few friends. However, there is an issue with using too much bandwidth if you try to host something through your public folder that becomes too popular. As per https://www.dropbox.com/help/45:

There are currently no hard limits on public bandwidth usage. We do, however, have an automated system for detecting and flagging unusual amounts of bandwidth usage. We will send an email notification whenever an account is flagged. Once flagged, public links will be temporarily disabled and users who use the links will see an error page instead of your file.

I had a similar issue, but in my case it was purely a misunderstaning of the Dropbox UI.

When you click the link in the email you get when someone shares a folder with you, there is a "Download" button up at the right on the website you come to (see this screenshot). I thought that button meant that I would download the files once to my local drive – while that is true, it turns out it was also the way to add the folder to your Dropbox.

In case you too missed the function of that button, just click it and select "Add to my Dropbox" (again, see the screenshot).