Doctor Who: 12 Cool Details Revealed In Steven Moffat's Blink Commentary
10. Weeping Angels Often Attack People Who Are Sleeping
Speaking of easy targets, sleeping humans must be the Weeping Angel equivalent of fast food. They don't have to worry about their victim beating them in a staring contest, or holding up a mirror to lock them in place. They can just waltz right up to their unconscious and defenceless prey, and give them a quick zap.
And apparently, they do this quite a lot. Early in the commentary, Gold asks if Angels like to go after sleeping humans, and Moffat - in a somewhat tongue-in-cheek fashion, but hey, that's just how he talks - confirms that they "frequently" do.
The writer also added that missing people are "people who slept in the vicinity of a Weeping Angel". Thanks for the nightmares Moffat!