In the interest of being political, I will not expound upon the fault in your description of the problem. Suffice it to say that it's hooey. RAID isn't magic, and it isn't terribly complex. You add drives to an array, and that's handled by the drive controller. Most RAID controllers wipe the drive clean when you create an array, which would have destroyed all of his data. It wouldn't have just been "corrupted". I can think of maybe two scenarios where there might be "telltale signs" of a failed attempt to create a RAID array, but neither seems to apply in this case.
Regardless, for some reason, your story piqued my interest, so I went ahead and searched on your customer's name. The first article of significance I came upon was this:
http://www.complaintsboard.com/complaints/nerds-on-call-c443471.html
It was on the third page of a Google search for the name listed in your "original source" link.
I'd say his claim seems to back up my suspicion - the technician(s) assigned were not competent, and for you to come to a place where geeks hang out and try to besmirch the name of a customer for whom it seems the service was not just poor, but HORRIBLE is a smear on your own name.
I'm not going to continue to chastise you. I imagine your fears of actually having to pay for the mistakes of one of your techs (or yourself) are enough to worry about without having your peers tell you the ways in which someone screwed up. My best advice is that when this actually goes to court, since it seems the man's disability claim has been affected and he'll need money on which to survive, let your lawyer do the talking for you.
The one other claim that you linked (where a clerk gave him brake fluid instead of power steering fluid) does not constitute "a lot of 'mistakes'".