Apple awarded patent for touchscreen slide-to-unlock gesture

How is something that seems so obvious and trivial patentable? In the physical world this seems like patenting doorknobs that rotate to the left versus the ones that rotate to the right that everyone was already using.

prior art? <a href="http://goo.gl/Wvv6l" rel="nofollow">http://goo.gl/Wvv6l</a>