I am aware of 3 problems in this space. Firstly people having the same surname and even first name. Ironically this tends to hit people with rare name, someone called John Smith is a known problem, but Winston Fortescue-De'Ath is bound to have a duplicate somewhere (we occasionally have this problem inside the NHS incidentally). Agent makes a simple mistake. Secondly there is a way of pulling a reservation by just typing the first few letters of the surname, and sometimes the agent makes a simple mistake there too. Finally there is the old jammed paperfeed issue. The boarding pass issued to the second passenger of the day is the screwed up boarding pass of the first passenger that got jammed when the printer warmed up. Printer reprints the boarding pass again. Passenger1's boarding pass is handed to passenger2, passenger1 goes for a coffee somewhere, then proceeds to security T5. FLY says no-go since passenger2, not having his spectacles on, has already blissfully sailed into Flounge. Worst version is when several passengers in sequence wander off with the wrong boarding pass.

Since the sky didn't fall in I would leave this as an almost interesting discussion point over evening supper parties.