Airline Security and Lost Luggage

Reports today that BA lose more luggage than its European rivals prompts a moment of extreme disquiet.

If you look at the policies of the airlines it is clear that baggage reconciliation is the backbone of airline security. Roughly speaking it means that if your bag is on the flight then so are you. Not 100% certain in an age of suicide attacks, but still adequate as the main strand of deterence.

How then can a bag go on the wrong flight, because that would mean that 2 flights would have taken off with their baggage reconciliations wrong?

Perhaps someone from the airlines could enlighten us