fwiw, you don't need to turn it off to install unsigned apps, it can be overridden on a case-by-case basis by right clicking the app and opening it there. you are never prompted again for that app.

i can see the argument for "burying" this ability, as users will tend to just get used to clicking "OK" blindly if you give them the ability to dismiss a prompt like this, much like i find myself doing with UAC on Windows.