Facebook's just introduced a couple new security features for user accounts — after all, the more secure you feel, the more you'll share. The first is straightforward: app passwords allow you to generate custom passwords for any app that might want to access your account — this keeps your main password secure.
Facebook describes the other new feature, trusted friends, as "giving a house key to your friends." If you're locked out of your account and unable to perform an email reset, the system can send an access code to your pre-chosen trusted friends. It's a relatively specialized feature, and you'd better really trust those friends, but it may well come in handy... sometime. App passwords are available now, while trusted friends is currently in the testing phase.