In a pretty sizable (and weird) security bug, Apple's Smart Cover can be used to unlock any iPad 2, even if there's a passcode on it. Here's how it works.
As you can see in the video, it works like this:
- Lock a passcode enabled iPad 2.
- Hold down power button until it reaches the shut-off slider screen.
- Close Smart Cover.
- Open Smart Cover.
- Click cancel.
I don't know how anyone would've figured that out but it definitely works. Going through those steps exposes an iPad 2's entire home screen and apps (you can delete them but can't open any apps). Perhaps more damning is that if you have an app open before you lock it (like Mail or Messages), the user who broke into your iPad 2 will have full access to that app (and can see and send messages). The smart cover break in is limited, yes, but could be used maliciously to peep e-mails that weren't supposed to be peeped.
The only way to fix this bug is to disable smart cover-unlocking in the General settings menu.