That's quite possible. http://www.cs.columbia.edu/CAVE/projects/face_replace/

I can imagine someone turning the technique into a novel form of image compression, maybe for surveillance databases or something.

A very tech savvy friend bought a camera in Japan and after about a week or started delving into settings. He thought all the faces looked wrong. He found a setting that made the eyes bigger and rounder. It was subtle, but quite funny at the same time.

Most of the consumer compact cameras have a "purikura" setting or a "beauty" setting with special treatment for the skin, whiter eyes and whiter teeths, and eventually bigger eyes and smaller mouth (yes, that's a thing).

It may be on by default for the cameras targeted at a female audience (in a rapidly shrinking market, female bloggers for instance are a big target), otherwise it won't even be available in more specialized or "hardcore" markets, like DSLR or mirrorless (4/3rds, Nikon 1, EOS M etc) for instance. For the anecdote, I bought a shockproof/waterproof compact camera last year and there's nothing so fancy on it.

Eigenfaces

http://en.wikipedia.org/wiki/Eigenface

Think how someone could falsify your entire life...

Then realize you shouldn't define your life based on some digital records.

I don't define my life based on some digital records. But law enforcement (or the executive branch of the US Federal Government, including the NSA) does. And therein lies the problem.

Someone will be convicted (perhaps even without the intervention of a court) based on unimpeachable but falsified digital records.

That sounds like the fly in the printer at the start of (the movie) Brazil.

Which of course leads to the conviction and torture of an innocent....

The fact that this conversation is taking place makes it unlikely for those records to be regarded as "unimpeachable".

Accept it as an inevitability and develop skills that enable you to adapt, react & procreate in a multitude of diverse situations.

With personal video recording (a la Google Glass and friends) it won't be long before we're subjected to this sort of thing. It's amazing how close we're getting to Ghost in the Shell and I'm sure it won't be long when live video feeds can be hacked in real time to show something contrary to what's actually happening.

  and I'm sure it won't be long when live video feeds can be hacked in real time to show something contrary to what's actually happening

Done! Actually a few years ago. Even though I suspect that you have something more complex in mind then splicing in a TV signal:

http://www.geek.com/news/czech-nuclear-webcam-hack-included-...

https://vimeo.com/29279198 real time face substitution