Ted Ts'o has posted an
update on the widely-reported ext4 corruption bug. There are some
ideas regarding what could be causing the problem, but the bug hits so rarely that the developers involved have not yet
been able to reproduce it. "The evidence at this point points to the
bug requiring a combination of issues, perhaps certain hardware, certain
mount options, and perhaps needing to win (lose) a race where you crash
just as you are trying to unmount the file system."