The system could still fall over. Someone gets the booking code, prints the boarding pass and turns up as John Smith - actually being called John Smith and having the ID. The real John Smith turns up later, and who is to say which is the one who really is the correct pax? Especially if the real one was travelling on a ticket paid for by a travel agent. It's an unlikely scenario, but with common names, could cause absolute chaos, especially when the number of check in staff have been reduced. Do the systems accecpt multiple pax with the same names - say three or for totally unrelated John Smiths on the same flight?