NASA said today that the likely cause of the PAL-ramp foam coming off Discovery's tank was workers damaging it either by cutting it while working nearby, or leaning against it and cracking it. The loose blanket under the window had shoddy stitching. The bits sticking out on the belly tiles were improperly glued.
The shuttle is the most complex machine ever built - over one million pieces, each one delivered and assembled under government contract by the lowest bidder.
I used to think that was funny.