I think upwind and downwind present two cases here. Going upwind and falling off you can get the boat to slow, capsize, or round up by being tethered or having the sheets release. Going downwind, different story. In my case the crew was locked in trapping off the back, and couldn't get to the tiller. The boat turned downwind, depowered, and eventually capsized due his weight on the trap. By then it was a significant distance from me, and once on its side it kept moving. I've since taken to being hooked in to the trap even when I'm on deck driving downwind, at the very least it helps me feel more stable and less likely to pitch off.

The other thing I've experienced is having the crew's trap break, dropping him off the boat. The wind and swells were up, and my ability to get close enough to him to get him back on the boat was limited. This is the case where the throw bag that keeps being pictured would be good to have on board - you only need to get close enough to toss a line.