Anyone who's cycled for any length of time has heard countless variations on the "clipless newbie falls over" story. Mine happened as I pulled in to a gas station with my dad for a snack stop, successfully unclipped my right foot, put it down on the curb, and promptly lost my balance to the left, falling on my still-clipped-in side. My cousin rode into the yard of a woman he hoped to impress, rolled to a suave stop right in front of her, forgot to unclip, and faceplanted into the grass. It happens to everyone, each in his or her own uniquely humiliating way.
Falling down at speed during winter cycling is also so common as to be boring (at least in the Midwest, where winter equals snow and ice) -- and assuming you can hit a soft snowdrift, it isn't so bad. However, when you mix studded snow tires into the recipe, you get a variation on the low-speed clipless pedal Fall Down Go Boom (FDGB) I like to call the Overconfident Dab and Dump (ODD).
No clipless pedals are required for the ODD. In fact, flat pedals and regular shoes increase the overconfidence factor, making an ODD even more likely. All you need is a set of studded tires and enough riding time to get very accustomed (perhaps TOO accustomed, he said, ominously) to the traction they provide. Soon, you're gleefully zipping over black ice like it's bare asphalt in July. You laugh at the elements. You're untouchable. You even find yourself looking for the icy spots and aiming for them, just so you don't wear down your pricy studs on the rare stretch of bare pavement.
Finally, you have to stop. Maybe it's for traffic. Maybe you need a coffee. Maybe there's someone you want to impress with your devil-may-care "cold? what cold?" attitude. So you hit the brakes, bring those studded tires to a halt, gracefully remove a foot from its pedal, and place it on the ground -- forgetting that, unlike those tires, your shoes have no studs.
Face, meet ground. Oh, and the bike's now on top of you, too, just to add insult (and maybe more injury) to injury. But hey, at least you provided some much-needed perspective for all those people in their warm cars who are now thinking, "My commute may suck, but at least I'm not that poor bastard!"
If you ever need motivation to practice your trackstand, one ODD will do the trick.