You are lucky - the user of one Linux PC that I manage had an unfortunate habit of nudging the reset button when sitting down ... This is rather a pathological case but it resulted in serious data loss on two separate filesystems on different physical disks (one PATA and one SATA), despite no actual power loss. I was using an ext3 plus LVM setup and I'm convinced that the use of hard disk write caching was the problem.
http://lwn.net/Articles/343425/ has more details. Haven't had any more problems since stopping use of write caching and making some other changes such as ext3 data=journal. I also stopped using LVM but I don't think that's a factor - on other PCs I now just use data=journal and turn off hard disk write caching, and still use LVM.