A friend of yours (who could well live on the other side of the planet) manages to get 'return' tickets such that someone can have 6 hours anywhere they like on the planet before being returned to their origin point.
One ticket to anywhere in the world, for you. You go to ... ?
Two tickets, for you and a friend to go anywhere in the world, return to respective start points. The two of you meet in ... ?
One ticket, for someone else to visit you. The person coming to see you is ... ?
One ticket, for someone else to visit a third person. Who do you send and who do they end up visiting?
I don't even remember what started me thinking about this, apart from the obvious fact I've been watching Star Trek: Deep Space Nine for the past 5 ½ weeks. And my sister was visiting from Australia for the week just been.