Well, I'd say a good place to start thinking about this might be to recall the circumstances that led to those people dying, and use that to inform your estimate of how dangerous a particular situation might be. For example, if you're mired in a snowdrift in mountain country during the winter, with a blizzard on the way, staying put is probably the better bet. If you're stuck in an irrigation ditch in farmland during the late spring, on a sunny day, looking for help is likely safe and may -- depending on where you are -- be faster. Being slightly paranoid about unfamiliar territory (like desert) is probably a good idea.

As a general policy, I think I'd be likely to go look for help if and only if I knew I had a good chance of getting somewhere I was significantly more likely to find that help, taking local conditions into account. Keep in mind that you're probably a lot more likely to successfully flag down a passing car if you're standing next to a disabled vehicle at the time -- and especially so if the vehicle's got some obvious damage.