My phone had fallen off of my lap and onto the floor while I was sitting on the couch. I wasn't using it at the time so I thought, "That's not the most dangerous place to leave it." As long as I remembered it was there.
Well when I went to get up, I put my foot right on top of it without knowing and in the process of sitting up straight I put enough pressure on the back of it (it was face down) and the next thing I heard and felt was a small "pop."
My stomach dropped and I was slightly in shock.
The repair went very smoothly thanks to the teardown on this site and a video on YouTube that showed me how to take apart every little piece of the phone.
Make sure you check that your buttons work before securing anything back down. The power button that came with the replacement was a little too short and wouldn't spring back when pressed. I just used the "old" power button.