Interesting, but from your description it sounds like if I can get my hands on someone else's Chromebook I can still put it into developer mode and install my own software on it, right? Sure, this mostly prevents someone from using a Chromebook that someone else installed malicious software on, though if that other person had time to open the case they could even get around that. But this doesn't solve the case of I have a device with private info on it, you get the device, and want to bypass the security measures on the device to get at my data. Or in other words, it doesn't solve the situation seen in the recent Apple vs FBI case.