Apple has had a lot of security issues as of late, one of them relating to its Apple ID "forgot password" system. It was possible for anyone to gain access to another user's account simply by knowing their email address and birthday. This lead to Apple taking down iforgot.apple.com until just recently.
Earlier this week, Apple took steps to strengthen the security of Apple ID by giving users the ability to turn on two-factor verification. It's recommended that all users turn this on, and Lifehacker has more on how to do this: http://lifehacker.com/5991797/apple-adds-two+factor-authentication-to-apple-id-heres-how-to-set-it-up.