Do you think your iPad 2 is secure since you have a lock password setup? Think again. Anyone with a Smart Cover from Apple can unlock your iPad 2 without having to put in the passcode. Ok, so while it’s technically true that they can unlock the device, the device itself still thinks it’s locked and won’t let you launch any applications. However, if you locked your iPad 2 while you were in your mail app, once the person uses this technique to unlock your iPad 2, they’ll be able to see everything within that app since you never closed it. So again, while you can technically unlock the app, you can’t launch any apps, but you can use apps that were open when the device was locked.
This seems like a fairly big security bug that Apple will most likely fix now that it’s out in the open, but since you can’t really launch any applications while doing this, I don’t see it as a huge problem. Just make sure you go back to the home screen before you lock your device if you’re really worried about it.