Re: Long live tape !
"Though you might have the tape in ten years time, the cost of the drive to read it becomes prohibitive quickly. Given that it's supposed to be your insurance against disaster, having to source another compatible tape drive rapidly, installing the software, restoring from the tape, etc. can take DAYS."
it sounds like you're envisioning a restore of 10 year old data to recover from a disaster. There isn't an organization out there that can survive rolling their business back by 10 years. The exact timing of the change is debatable, but 10 year old data is an archive (for reference), not a backup (for restore/recovery/resumption of business).
Not to mention that Backup/Archive Management Systems have provisions for migrating data to new media. So you wouldn't have data you need quick access to on media that you can't access quickly.
"I'm sure in large datacentres, etc. the regime is different..."
Yes, yes it is.