Say you have a picture that's 1000 pixels wide x 1000 pixels tall but you have a place to display it that's only 1000 pixels wide x 500 pixels tall. What to do? You basically have two options: 1) crop the photo and leave out the least relevant parts or 2) squash it and make everything short and fat. What's the diff!?!
The best example of this is when your (least) favorite establishment plays sports on a widescreen TV that's designed to play on an old 4:3 TV, making all the players short and fat. The difference is large enough to think "man those guys are kinda fat and funny looking" but not big enough to be totally confident those aren't the right proportions. Bye bye conversation! Hello anal retentive internal debates about whether the TV is set to the correct aspect ratio!
I recently walked through a graveyard and saw a tombstone with a photo of the deceased. It looked like it was at the wrong aspect ratio but in the end I think she was just overweight. May my tombstone have a correct aspect ratio image of my likeness.
And may my lab page have faithful representations of my students' and postdocs' height and width: http://www-personal.umich.edu/~parent/personnel(new).html