I have probably posted mine here before, so I will do the short versions:
1.) The reason I almost ALWAYS DM: I was only about 11 or 12 years old and learning to DM. I had recently run my first session and one of my 2 players was DM'ing a few days later. He was an experienced DM and about 2 or 3 years older. The other player was also in high school. During the session, the 2 PC's were separated and my PC was transported to the Abyss to face a demon lord (Demogorgon, IIRC). He captured my PC and bartered me off to another sinister being. At that point the other player moved to block the door and I was told that to teach me a lesson for the rules I had interpreted incorrectly during my DM'ing session a few days earlier, as well as those in character creation for this guy's game, I would have to complete some "tasks" for this being. They included holding the other player's hand while singing a love song to him (in RL, not in game), etc. I was called all sorts of things and my exit was blocked by these two older kids. They left the room, locking the door, to get some things for their scheme and I climbed out the window before they came back.
2.) Due to the above, as I said, I almost always DM, I allowed myself to be talked out from behind the screen about 3 or 4 years ago. The game started with the PC's (there were 4 of us) naked in a ceremonial chamber with the village elders around us. There was a fire burning in the center of the room and we were all ritually scarred with a "soul knife" that drained our Con and took a bit of our soul (as a rite of passage). We were then given a backpack full of rocks and sent out unarmed and unequipped to survive a month in the wilderness. The party got split up and I and another player had our PC's at the edge of the valley, in the mountains. We saw a sheltered ledge and tried to climb. We both fell (remember, our Con scores are drained permanently) and my PC is down to 2 HP. The other PC is unconscious and dying. Then, we are attacked by a pair of wolves. I have no weapons and if I run, the dying PC is dog chow. We both handed our character sheets to the DM and planned my next game. That DM was very unfamiliar with the rules of 3.x, having mostly run Storyteller games.
DM