I would draw the line at what the device's technical capabilities are, not what I am "permitted" to do.

If you use permission in your definition then it becomes impossible, by definition, to restrict the use of a computer. If Dell's next cheap desktop was locked down like Apple locks their devices down, would you buy "Well it's not a computer you know, since you are not allowed to run what you want on it."? No, of course you wouldn't.