It's still slightly problematic for me. To prevent the re-activation of DMA, I have to disable the Guest account. Unfortunately, this also disables the "Find My iPhone" application. I would like to have both. Is there a way to have the Guest account, but not let people log into it when the machine is locked?

EDIT: Got it. It reactivates the Guest user when you turn on the "Find My" feature, but you can deactivate Guest user afterwards.