No, I have not blown one up. No, I have not witnessed one blowing up (except for one Turbo 400). Yes, I have spoken to car owners and drivers who have. Injuries vary from light discomfort to actually loosing body parts, big medical bills and lost wages. Not to mention repair bills to the car. Reasons for these events happening are also varied. Improper operation, symbiotic drive train component failures. Although this problem maybe more acute in a 727, other manufactures (GM & Ford) are not safe from total transmission explosions either. Truth is, there are many reasons why transmissions fail. Not just the ones mentioned here.
One member here mentioned applying ballistic material to the floor of the car. Why won't this work? If the ballistic material is applied to the inside of the floor the parts are still going to come through the floor! Only this time you will get hit by the parts including the ballistic material. Considering the weight and kenetic energy transmissions store this is not something you want to be hit by. Containing the explosion and the spuewing of parts has to be contained at the source. This is why NHRA/IHRA and other racing sanctions endorse the SFI Foundation's decision that requires the transmission containment system be applied to the transmission case itself.