I bought a Mid 2011 MacBook Air from CraigsList. I traded my unlocked iPhone 5 and added $250 for the Air, I am upgrading to the 5S so I saw it as a fair deal. Before giving the money to the seller, I checked it out in Starbucks, where we had met. It connected online and everything seemed fine. I gave the money and we went our separate ways. I didn't get a bad vibe at all and he appeared to know his stuff, Apple-wise. When I got home and connected to my wifi, the computer rebooted and a iCloud lock screen appeared. Given the harsh word expressed on the screen, I can easily tell that this MacBook was stolen. Before this happened, it booted up just fine. But now, I get the iCloud 4 digit pin lock screen. And the EFI lock whenever I try to boot using a external drive or thumb by pressing the option button. I took the MacBook to the Apple store and explained my case, and they said they couldn't help. Since I am not the original owner, I do not have proof of purchase. So, they can not send it to their engineers to fix bring it back to original factory settings. I then asked about the original owner, is there a way I can find out who he or she is so they can get their stuff back? The Apple "Genius" told me that I should just take it to the police station to see if it is reported stolen. I am not going to the cops. I tried telling Apple and thought they could be of some help, but they weren't. I even asked if they could contact the registered owner or something and the guy just said take it to the cops. I refuse to have given away my precious iPhone and $250 of my earned cash for a beautiful paperweight. So, after doing some research I think I found a solution and would like some verification to know if it would work. If I removed the SSD and use a enclosure to connect to another Mac as an external drive to wipe it completely clean and install a brand new OSX. And then reinstall it on the Air, and use a brute force technique with a Teensy USB Development Board....wouldn't that solve everything???