Meh. We live in a world where text and images are completely untrustworthy. Why is video such a big deal?
I mean they can accept just about any kind of special effect in a movie as being possible, but editing videos to swap faces is a huge stretch?
I do believe that some people will fall for them, but the damage won't be any worse than when people fall for shopped images and phishing emails. It's just something we have to deal with.