The fact that you are still asking these awesome questions are going to get you props from all of us here brother. Shows that you want to learn and just don't want to get it spoon fed to you.
I would definately put the obese patient down as a candidate, especially an extremity that gets caught under their weight after they fall and are unable to get up on their own.
Depressed patients, I'm not so sure.
What about the stroke patient who falls, lands on the affected extremity and is not found for 2-3 days or even 6-8 hours?