Well, I’ve seen how my friend unlocks his HTC Hero phone and all… And it is an interesting way to lock\unlock a phone.
So basically, if your finger is greasy, you can easily give out your passcode without knowing. Like, handing over your phone to a friend to hold it while you go answer the nature’s call, you come back and find him tampering around with the phone and maybe just snatched an account or two to write embarrassing facebook status.
Yea… Better be careful… Don’t unlock your phone after\while eating Kabab xD
… or just wipe the screen after (un)locking it!
But that’s a very interesting point-out!