[peterwwillis]

Since a video is just a string of images, all the attacker would need is a sufficient number of photoshopped images to show a series that (when stitched into a video) shows the user blinking. I'm pretty sure you could make a Photoshop plugin that would do this.

I'll do you one better: you could probably make a print-out paper 'mask' of a person's face and just blink yourself, or something similar. This kind of tech isn't always as smart as we think.