Continuing the Australian theme, arriving at Brisbane we always entered into the FMC the radar vectors that we thought would happen rather than leave in the flight-planned route to the BN that never happens.
Inevitably one day we followed the "vectors" by mistake, and needless to say ATC barbequed us in a way that only Australian ATC can do. I still think that we were deliberately trapped by ATC, but that's not the point.
I believe that the FMC is best programmed for what is likely, otherwise stupid things happen like you end up overhead Budapest at 20000ft. But you have to be SO careful.