Why is my pubic hair missing? No, I /don't/ remember where I put it!
Mac users should by now be convinced that PC's are better. Except that on a PC *.gif files won't have the pretty little thumbnail that you get on a Mac. You'll get the dogeared-piece-of-paper icon on them, and then the Mac users will sit there waving their flippers like a thalidomide baby until you show them that yes, Photoshop will _still_ open the file (at 3x the speed).