Commonly most of us leave a set of keys for our home with someone else that we trust like a close friend or neighbour. This is to allow us to get back in to our home if we lock ourselves out, which can be easily done if you can lock that front door without the need for a key typically by flicking a thumbturn or pressing a button.
Facebook has taken this practice to their account-security procedures by allowing us to work with a “trusted person” to gain access to our accounts. Here, you let Facebook know the contact details of the three to five trusted people and if a lockout occurs, Facebook would send the codes to these people and you contact these people preferably via phone or SMS for these codes. This can come in handy with older people who forget their Facebook credentials or if someone’s account was hacked and the password was changed.
Facebook are in a position to do this not just because of them being a highly-popular social network but users are using their Facebook parameters to sign in to a large number of consumer-oriented Websites and mobile apps. I wouldn’t put it past Microsoft or Google to implement this in to their account systems, especially more so with Microsoft using the Web-hosted credentials as the key to our Windows 8 computers.