An enterprising and brave college student hung a hammock in his dorm room with duct tape:
I attached 4 strips on either side to the ceiling, making a loop at the bottom. I then used some clothes line and 2 carabiners to attach the hammock. The whole setup can hold my 200 lb friend (he fell asleep for 4 hrs in it). Under that stress each strip is holding around 25 lbs (assuming the weight was equally distributed, which I did my best to do).
I wouldn't recommend trying this at home, but it is a good indicator of just how strong trusty duct tape really is. (See also: how to make a duct tape wallet.)
Duct Tape stress tests [MAKE: Blog]