Mobile OS security models are bound to land on the desktop soon-ish. What does any random App have to do with anything in ~/Library that is not its own Applicat

Mobile OS security models are bound to land on the desktop soon-ish. What does any random App have to do with anything in ~/Library that is not its own Application Support or .plist preferences? To be honest I don't mind if all Apps are sandboxed with the exception of a couple "user super-user"; I don't really care if my machine's root account is secure if all my horses sitting in $HOME are let loose on the net.