DropBox is denying that they were hacked, but hundreds of usernames and passwords showed up on PasteBin. DropBox says a third party leaked the information and all the passwords have been expired. Here is the full story Hundreds of Dropbox passwords leaked online but Dropbox denies it was hacked.
This comes after a warning from Eric Snowden about Privacy and DropBox, Facebook, and Google. Here is the article from PCWorld. In this article it shows alternatives to the popular service.
In addition Eric Snowden released this video “Here’s How to Take Back the Internet” March 2014