We probably want to have different policies for different kinds of devices. For mobile, pruning unused storage is definitely important, but for modern desktops with >1TB drives most users probably won't ever need to "free up disk space" unless they're hit with some kind of denial-of-service attack, in which case policy should focus on preventing the latter. And this is going to get more true over time.
Rob -- "He was pierced for our transgressions, he was crushed for our iniquities; the punishment that brought us peace was upon him, and by his wounds we are healed. We all, like sheep, have gone astray, each of us has turned to his own way; and the LORD has laid on him the iniquity of us all." [Isaiah 53:5-6]
