I think I'm using a more liberal interpretation of what deprecate means, but it doesn't matter - we both mean the same thing - redundant, pointless, once relevant now no longer relevant.
Good point in the irony - though I wonder if their protectionism is driven by agreements with content companies that allowed Sony to defend BluRay in the first place? After all the hardware manufacturers shouldn't care much about how their hardware is used, unless they need help from the big studios etc. to push their hardware formats.
Minidisc was an affordable recordable digital format before CD burners became prevalent. DAT was better though as it was 16 bit, 48KHz. Minidisc was a lossy compressed format, though it wasn't a total flop.