[IGGUS]

It may also have something to do with the resolution of their pic.

If you put 2 identical pictures on your phone, one is 20x40 pixels and the other is 200x400, when you associate the pics with a contact two different things happen. Choose the larger one and you're brought to a screen where you can choose the area to be cropped out. With the lower res photo it just centers and you never see the cropping screen.

Do you have that issue with every single facebook pic? Maybe it's that the pictures are downloaded off the tiny thumbnail instead of the higher res photo that's behind it.