Apple is implementing a security feature known as two-step verification. It's similar to the security measures used by Google and other web services. Users are able to enable the service through the Apple ID website, after which two-step verification will be required to make changes to a user's account.
Users will set up a trusted device, such as a Mac or iPhone, and will need to print a recovery key. In order to reset a user's password, they will need to have access to the recovery key that they printed out. The first time you attempt to buy an app on a new device, you'll be required to enter a pin that can be accessed from a trusted device.
You can head over to the Apple ID website to enable it for yourself. It's definitely recommended, though it's only currently available in the United States, United Kingdom, Australia, Ireland, and New Zealand.