You're quite correct that a virtual machine could make some use of it. If we have an
interface to the filesystem that allows us to punch out blocks (see eg
http://techpubs.sgi.com/library/tpl/cgi-bin/getdoc.cgi?co...) and use sparse files, we could "overprovision".
The software that emulates an ATA device can probably be changed about as quickly as real ATA
devices -- remember drives are full of firmware too. The holdup is getting T13 to decide on a
command number and publish ATA8. Then it's a 'simple matter' of getting users to upgrade ...
and I think a large number of them are going to be wary about further updates from at least
one major virtualisation provider from now on.
Oh, of course drive vendors aren't typically quick to publish microcode updates. You've
already bought the drive, so they have little to gain from giving you firmware updates, and as
every firmware update is potentially dangerous, they have a certain liability there too.