My brother has his 16', 48" collapse. He had a leak around the return that he ignored. It eventually caused rust, and then the pool failed at that point. There were three kids in the pool at the time (10 y/o or so) with adults watching them. It opened up, the water ran out, across his backyard, and down his neighbors driveway, taking along with it the approximately 2 yards of topsoil and seed that his neighbor had just installed.
Luckily the wall opened slowly, so the kids had time to react and get away from it, while the adults got them out of the pool. Nobody was hurt, and aside from some new topsoil and seed, nothing was damaged.
-dave