Why bother with a lockscreen at all. Unless you want to password protect it, I see no reason why the device can't just always be logged in. Upon hardware power-on I want it to shoot directly to the web browser or whatever I was doing last.
Because devices will accidentally wake up when in a pocket / bag / etc, and you'd prefer not to feed random touch events to whatever program you're running. Of course sometimes this won't be relevant, and you could do away with the lock screen. E.g. the Eee Transformer requires the usual Honeycomb unlock gesture when it wakes up undocked or in the dock by pressing the power button, but not when it's in laptop mode and is woken up by the lid being opened.
