Isn't it a little hard to accept that it isn't a value judgement when we generally have a lower value of things that have rusted?
I think the original comparison to 'spinning rust' was tongue-in-cheek and not meant to be taken so-very-seriously, but it's kind of taken on a life of its own and, personally, I feel that it's gone a bit far and undeservedly undervalues hard drives.
The earliest use I could find is more inline with my observations of matter-of-fact usage than a joke taken too far:
"Logically, if you utilize a 'memory' disk you are ridding yourself of the physical limitations of disk drive technology — basically trading in the spinning rust. In a disk drive, you are battling physics to squeeze more performance out of your array; there are certain physical properties that just can’t be altered on a whim." - 2004
I think the original comparison to 'spinning rust' was tongue-in-cheek and not meant to be taken so-very-seriously, but it's kind of taken on a life of its own and, personally, I feel that it's gone a bit far and undeservedly undervalues hard drives.