This was something I really picked up on a couple of weeks ago when I had to take a couple of flights as I was coming back from holiday.
I’m assuming you all know what baggage carousels are. Certainly if you’ve ever checked luggage for a flight you will presumably have stood at one at the other end of your trip (unless you weren’t really that bothered about your luggage anyway).
For the benefit of those who’ve never had the sheer joy of experiencing the safest way to travel (and most tiresome way to spend the last hours of a vacation), here’s a picture that neatly includes the key elements.

The key thing about the baggage carousel is visibility. Passengers need to be able to see their luggage, so they can take it away, and gradually empty the thing. And what’s the best place for you to both see and pick up your baggage? Why, right next to the carousel of course.
Except, if everybody stands right next to it, suddenly your visibility goes isn’t so good, because there are now people to your sides blocking your view down the length of the carousel. And anybody standing back from the carousel at this point won’t be able to see anything at all, for the mass of bodies.
It struck me that it’s sort of a Prisoner’s Dilemma. Overall the best results for me are going to be if I stand next to the carousel – then I will either have great visibility and be close to the luggage (if everybody else stands back), or poor visibility and be close to the luggage (if everybody else stands close).
The worst result of all for me occurs if I stand back (no visibility, and having to walk to the luggage, if everybody else stands close), and even the “best case” for me there is just great visibility, though having to walk forward to grab my luggage.
So my self interest says I should stand as close to the carousel as I can, even though if everybody agreed to stand back behind the yellow line (like it bloody tells you to do anyway) we would all get the second best possible results and everyone would have a better and more pleasant experience.
Incidentally yes, I did think all of this while I was stood back from the carousel. Having already been awake for over twenty hours and having had a nine hour flight followed by another hour flight, I was in no mood to jostle my way forward and fight for a position amongst the annoying self-serving idiots that I had already be forced to endure at close proximity in a flying metal tube.
I hate flying.