An interesting technology to consider concatenating with this is the emotional manipulation potentiated by pulsing of emissions from monitors, revealed in the '90s patents of Henricus Loos. It may be that a majority of people will be both unaware of these technologies, and unable to resist drinking the koolaid doubly served via altered video.
Another thing I've not seen discussed in these examples of the Face2Face software is audio editing, which can take phonemes from recorded speech and create new speech from the phonemes.
Your point about the blockchain is about the only thing that provides a degree of assurance that this technology isn't apocalyptic politically.
The movie 'Running Man' prophesied how these technologies can be used rather trivially to destroy a person. In politics, the propaganda uses are not trivial, but dire. My takeaway is that I will no longer accept that video is evidence of anything.
Thanks!