I just upgraded my itunes this week and had to agree to a waiver that stated that my password was still valid for 15 minutes after purchasing an app. What that means after reading fine print, is that I download a free app and let my kiddo play on it and she hits yes to buying things, I am held responsible for whatever she spent.
I have every restriction in place and we tested it and she can still buy things (only spent $1.29 on a song I wanted to test it) for the 15 minute window.
Really sucks it has this flaw because with Kids that have their own ipods the risk increases for them to buy something.