While I was the tech with the uh-oh, I can legitimately roll out the 'I was only following orders' defence.
Called out of hours to a hospital server which was flagging a predictive fail on one disk in the RAID array (I forget the exact disk size, either 36 or 72GB)
It was a HP DL380 G4 which had 3.5" SCSI disks installed and one was indeed flashing amber to indicate predictive failure.
On the phone to the support team I was told they'd down the server for me so I could replace the failed disk (it's not necessary, they're hotswap, it's actually better to hotswap them), I agreed and proceed to boot the thing from a HP utility disk which allows me to check the RAID config, disk serial numbers, model numbers etc. (it wasn't unknown for disk caddies to be re-used by parts brokers and have incorrect markings compared to the actual disk in the caddy)
I found that some genius had configured the disks as a RAID0/JBOD, essentially a bunch of disks with a container spanned across them all to give a disk the size of the sum of parts, in this instance they'd done something I didn't realise was possible and had allocated the first 10GB of all the disks to the JBOD to give a disk size of 40GB for the OS (server 2003 IIRC)
They'd then allocated the rest of the disk space to a RAID5 set to hold the data volume (Might have been SQL Server, possibly Exchange, critical data anyway) so notionally the data volume was fault tolerant but not OS as removal of any one disk from a JBOD will kill it.
So, I explained this to the support team wonk who insisted he knew better than I, after all I was only a lowly out of hours tech (who happened to be HP qualified to work on Superdome, EVA, Alpha etc. etc.) and he was third line who knew all and requested I 'just shut up and replace the disk' or words to that effect, he was however happy for me to hotswap the disk so we booted the machine up, he connected remotely (genius things those ILOs) to 'monitor' my actions.
I protested, he demanded, getting quite stroppy and threatening to escalate it to his management. I suggested he dial their number and put us on a conference call so he did. Once I'd been introduced and explained why I didn't want to do it, his manager also insisted I replace the disk as he trusted his tech.
Obviously I then pulled the disk and watched the machine bluescreen instantly.
After what must have seemed an eternity to the remote parties but a few seconds to me, I asked 'would you like me to fix that for you?" and got a quiet 'yes, please, if you can'.
Turns out every server in the business had been built the same way.