That's a totally valid point. My guess it that they assumed most users would keep their phone in a pocket (since it's easier to tap than if it's buried in a bag

That's a totally valid point. My guess it that they assumed most users would keep their phone in a pocket (since it's easier to tap than if it's buried in a bag). In any case it's a big upgrade from people who leave their computer unlocked all day. I'd love to see them add automatic proximity-based locking.