Just over a year and a half ago, a "suitcase sized chunk of foam" broke off and did serious damage to the space shuttle Columbia. Hitting the shuttle"s left wing, its damage would cause the shuttle to break up on re-entry. The investigation into the disaster has recently completed its work, and has come to a conclusion on exactly what happened.
The Columbia Accident Investigation Board concluded that the fault was not with the foam, but with the way it was applied; by hand and stuck on with glue guns. The process left many places still exposed, allowing liquid hydrogen to seep in. As the hydrogen warmed up, it expanded, causing the pieces of insulating foam above it to pop off, with seemingly lethal force.
NASA officials commented that "It was not the fault of the guys on the floor; they were just doing the process we gave them." NASA are now attempting to get the fuel tanks recertified, and ready for space flight. The tanks now face tighter regulations. At $40 million per tank, they represent a massive investment for NASA.