It was brought to my attention a bit ago by a client that the iPad 2 with IOS 5 has a flaw that allows the last screen accessed before the Smart Cover lock was engaged.
This is obviously not good for those using the iPad for financial, medical or legal purposes.
The work around until this is fixed correctly is to lock the iPad while on the home screen or a screen which does not display anything of importance (Like “Please Stay Calm” or maybe “Angry Birds”).
A quick search turned up people talking about this on forums and a number of news articles such as this one from cnet.com.
There is mention of a security flaw with Siri that allows people to send text messages, emails and even make phone calls from a password-protected iPhone 4s lock screen.