It is absolutely critical to use data scrubbing with Linux software RAID. If you fail to do so, when one of the drives fail and the new one is put in place to resync with, the chance of losing all data is very high. When Linux resyncs a RAID array, it steps through each and every block on the disk(s) it is syncing from. If there are any bad blocks on the 'good' drives data scrubbing hasn't found (or data scrubbing isn't being used), that drive will also be marked as unusable. This renders your array useless unless an array is in use that can recover from multiple drive failures at the same time, or you have quite a few days to spend on manual recovery.
When I first saw this comment in my queue I almost deleted it thinking it was spam, the link being from Anonymous and with no description. It's actually an informative site with some valid points on issues with RAID.
Here is a more friendly link if you want to check it out:
Battle Against Any Raid Five/Four/Free