3) Mud Butt
If you've ground camped during rainy weather, you know what I'm talking about. Leaks and flooding are a real concern with ground tents. Seams fail, fabrics soak, and sometimes your bathtub floor ends up being a bathtub of water!
This adds up to you being cold and wet in the middle of nowhere. On a good day that's just super annoying, take it a step further and what actually happens is it lowers your immune system, on a bad day it could mean hypothermia.