Google for example makes it pretty clear that, given the complexity of their backups system, they'll never be able nor try to delete your data completely. I'm guessing most companies are the same, backups are essentially read-only.
This is a good point that I don't see repeated often enough. To expand, and rant a little (okay, really just rant...):
People whine about Google or Facebook's apparent inability to permanently delete data, yet simultaneously expect their data never to be lost due to bad disks, datacenter fires, or whatnot. It's all very silly. Of course FB or Google can't delete all your data, and it's that way because that's how everyone wants it.
Even if a backup is done in a trivial way, you really don't want to start messing in backups as part of normal operations. A simple bug can destroy the wrong data. Without a backup, that data is lost forever. And making a backup of a backup so you can mess in the primary backup completely destroys the usefulness.
I don't mean they should mess with the backup. Only that talking about deleting the data is not very productive since the data won't ever be completely deleted. What can be talked about is data usage, confidentiality or specific "deleting" mechanisms.
