Whether we're talking about Twitter, Gmail, bank accounts, or anything else accessible on the web, account security is no joke. As a result, we're starting to see more and more companies take advantage of advanced security methods like two-factor authentication, which requires the user to not only entire a username and password, but also a code typically send via SMS to the user's cell phone. This means that a physical device must be accessible, making it much more difficult for would-be snoopsters to remotely gain access to an account.
Several weeks ago, Dropbox suffered a small security breach that gave wrong-doers access to a few unlucky users' email addresses. On the good side, it also brought the vulnerability to the Dropbox staff's attention. Since then, they've been working hard to beef up security, and today, they introduced two-step verification.
Much like Google's two-factor authentication, once enabled this requires you to login using two different sets of verification: your password and a unique identifier sent in either a text message or generated locally on the device using the authenticator app (which you have the option to get via QR during the set up process).