My wife has helped me move STTNG, TZ and Demoman into the basement, but she has retired due to the fear it causes.
The only near-mishap I've had was when a friend helped me move my newly purchased TOTAN into the house. There are a few stairs that go down into our living room and these are near the stairs down to the basement. My buddy guided me too close and one of the wheels of the dolly went off the top stair to the living room. I was able to bend down and pull on the opposing side of the dolly to slow the fall. My buddy was dumbfounded and just froze until I screamed at him to grab it.
If it had gone over all the way, it would have tipped down three stairs onto hardwood. I get the shivers just remembering it. I always try to have three guys total when moving pins. Not a fun job though, and I usually end up with two.