Do you know what amazes me? Why do people think that they can just step right onto a treadmill that is still going? I have witnessed this several times over the past week, and its fairly amusing to watch. If you hop off the treadmill for a quick break, to get back on it, you need to get on by placing a foot on either side of the moving belt, and approach it from the far end or at least middle, so that you have a step or so to adjust to the speed.
Instead, I have witnessed several people just try to leisurely step onto the end of the rotating belt. What invariably happens is that they awkwardly sway, and try to spread their arms out to catch their balance. However, by that time, it's too late and the treadmill has already deposited them back on the floor. So far, I haven't seen anyone face-plant, but I keep picturing it.
When you're already at the end of the running session and trying to keep up your pace, it's awfully hard to keep a straight face when the Weeble-Wobble to your left just got thrown on the floor!