I did lose data from a ZFS raidz pool once. The cause turned out to be a slowly failing power supply. (An expensive, high-end OCZ unit, no less, with a 5-year warranty. OCZ replaced it without argument. Had it been a lesser PSU I might have suspected it sooner... oh well.)

Of course no filesystem could have survived that. But I still could really have used a salvager (fsck). I actually recovered a couple of critical files by dd-ing blocks off the disks.