I saw that the other day and I tested it on one of the copiers in my office. It's quite scary.
But - this mainly pretains to copiers that have built in hard drives for cache (all like the large multifunction devices in the video). Most of your home use printers don't have this issue.
I have used numerous faxes that also have internal memory and drive.
I am sure anything transmitted over networks is subject to intercept and hacking.
Is anything actually encrypted?
There is a company called HushMail that was pretty good at encryption, especially for sensitive material, from a b2b standpoint.
However, they have come under great scrutiny for their cooperation with law enforcement agencies and turning over mail as well as users identities.
The problem is, and has been, when should law enforcement agencies NOT be granted access.
And, bottom line...nothing can ever be 100% secure.
The only way two people can keep a secret is if one of them is dead.