My experience too.Because of this thread I decided to passcode my phone. I thought that it would annoy me but it doesn't.
I do. My 2 year old son has figured out the slide to unlock feature. Guess I shouldn't have let him play Flick Bowling. :/ And he's managed to send a tweet/FB update using qtweeter. Now I'm set to lock after 5 minutes. Takes an extra 2 seconds and keeps his ninja fingers at bay.
I don't. My iPhone is alwais with me, I don't see any reasons to leave it somewhere, besides, what if I forget the password. you know, sometimes it happens.