Well... regardless... the person that made the booking is fully responsible...Did you ask for a security deposit? Do you have the right insurance? Did you check their ID at check-in time? If you wish to make some extra money its all good... but treat it as such, you are not inviting friends in your house... You are offering a service and expecting to be reibursed... Being friendly is one thig but offering frienship is another matter...
It has happened to me, the people that turned up were not the ones that made the booking... I called the person who made the booking and doubled my security deposit on the spot or no entry...It worked out just fine...
Airbnb will not penalise you for refusing entry to an unregistred guest, it will be treated as no show and you will still get paid. There are no refunds for not checking in.