> The machine owner should (through a demonstration of physical
> presence) be able to do whatever they want.
Nope. Physical presence does not equal ownership. We circulate laptops as library material. Do they get to do whatever they want? Oh heck no. And if the security tape over the screws is tampered with we fine em to cover our time reauditing the system.
How about a lab computer for library patrons. They are sitting at the console, so they install a new OS? Not on my systems they ain't, at last not without a screwdriver and some way to distract the staff.