I could just see someone losing that shim halfway up a climb fumbling with it with gloves. Hmm, my crampon could be tighter here, let's take a break so I can adjust it. Oh crap there it goes! Then you are screwed unless you can crank up one size on the connector bar thing and get it on your foot. The shim isn't falling out or anything, but give the opportunity and climbers will make it happen.