i just wanted to add that I am having problems with a custom RAID configuration that doesn't have any WD hardware or software. I bought 2 Seagate Barracudas and a Vantec Nexstar RAID enclosure and after setting everything up, experienced some of the same problems that have been reported with WD RAIDs. After transferring everything onto the RAID, the folder structure disappeared and disk utility said both striped drives needed repair, which ended in errors. After reformatting and trying again, my file transfers seemed successful for less than a day before the setup became problematic again. After trying the repair disk function this time, utility stopped and reported that "live file system repair is not supported". I don't know enough about RAIDs to really understand what all is involved and where errors can originate, but so far, it seems like it's possible that WD may not be the only factor in the equation here. Possibly hardware chipsets?
*update
After some investigation, I found out that the setup instructions that came with my RAID enclosure didn't include a key element that allows it to be recognized as a hardware RAID. After resetting, it was recognized as a single drive instead of 2 separate ones, and i was able to format it as a single logical drive. I believe my problems were caused by a conflict in the hardware RAID trying to run concurrently with the software RAID setup through disk utility.