A useful primer to Integer overflows/underflows
From a presentation by a security contractor on campus:
1 bottle of beer on the wall, 1 bottle of beer, you take 1 down, pass it around, 0 bottles of beer on the wall.
0 bottles of beer on the wall, 0 bottles of beer, you take 1 down, pass it around, 4294967295 bottles of beer on the wall.
Funny! But it shows analogies between software and the physical world are rarely good!