The fact that you are carrying on over SATA drives, means you don't even know what server grade means. Without any type of redundancy or proper enterprise controller, this can't even be considered a server. So calm yourself.
Quite wrong...I have a RAID 5 Array made from SCSI drives that I've been using for years. And furthermore, nobody said a SATA drive can't be used in a RAID array -- they are frequently. Your assumptions are ill founded.
Clearly this isn't a server, and Apple hasn't claimed that this is a RAID array, nor would I expect it to act as such. They DID however, claim that Time Machine would work with network drives (especially APE attached USB drives) and it wont. Furthermore they are using very fuzzy terms to imply enhanced reliability/performance for their product which simply isn't true. I will grant you they didn't put in the cheapest drive they could find (the WD10EACS, which is a variable rate drive) but they are making up some marketing double-speak that it was "Server Grade". Don't get me wrong, I've used several Hitachi Deskstar drives and like them. But when I built my last RAID array I chose Ultrastar drives, which are clearly the higher quality units from the Hitachi line.
Look I like Apple products, but when they are wrong, they are wrong. You and the rest of the sheep can blindly follow along "Baah, Apple always right, baah"