I'm reminded of a (then) Science Fiction story I read several years back. IIRC, a man was accused of assassinating a public figure. He was seen doing it by several million people on TV. The only problem was that he was completely innocent. His image as edited INTO the video in real time - the flip side of this process. His image was pasted onto the image of the actual killer so everyone watching on TV saw him raise the rifle, pull the trigger and run away.
Consider that this technology runs on a tablet PC. Think about how much computing power can be had for just a few thousand dollars these days (multiple I7 servers, etc). Think about all the other video editing technologies that are old hat these days - wire frame, graphic overlays, scrimmage line markers on televised football games, logo blur, etc. Consider every conspiracy theory video you've ever heard about.
Scared yet?