Just received this email from them:
We wanted to let our developers know about an upcoming change to the Public folder for all user accounts. In April, we launched the ability to share any file or folder in your Dropbox with a simple link. This new sharing mechanism is a more generalized, scalable way to support many of the same use cases as the Public folder.
After July 31, we will no longer create Public folders in any new Dropbox accounts. If your app depends on Public folders, we recommend switching to the /shares API call. Public folders in existing accounts, however, will continue to function as before.
Please email us at api-program@dropbox.com if you have any questions or concerns.
- Dropbox API Team
