Yesterday my boyfriend and I were driving, and out of nowhere one of our truck's (95 Nissan pathfinder) wheels pops off. Luckily he was driving not me; I had been driving earlier in the day but I am glad this happened when HE was drivin! We ended up spinning halfway around and coming to a stop on the opposite side of the road's shoulder, facing the opposite way that we had been going. We were going 35 miles an hour and it was a pretty busy section of road, right around a sharp turn.
It was completely terrifying, and we narrowly missed hitting other cars. To make it worse, our released wheel went flying at probably 60 miles an hour down the road for about 20 feet!! Amazingly, no one got hit by us or the wheel, or the flying brake disk thing (which vanished into a creek on the side of the road.)
We pulled out of it with no major problems. Mark found three lugnuts of six, put the wheel on, and we slowly drove 5 miles to the junkyard where he found a replacement brake caliper and we were on our way.
Please make sure your car and all its parts are in fine working order before driving!