A recent article at Kernel Trap entitled Data Errors During Drive Communication indicates that "An ongoing study on datasets of several Petabytes have shown that there can be 'silent data corruption' at rates much larger than one might naively expect from the expected error rates in RAID arrays and the expected probability of single bit uncorrected errors in hard disks".
This is an interesting read. I used to blame my computer problems on Random Alpha Particles. I guess I can now expand my horizons.