When I worked in film and video production, I used visualisation all the time. In film, sketching things out on paper is critical to saving yourself a ton of headaches - and money - later. I drew storyboards, once taking one down as dictation while the director paced up and down and described the plot of his rap music video. I sketched out set designs too. I even sketched a design for a retail store once for a gentleman who needed to visualise how a new layout for a Gap store might look.
The thing about using this technique for prototyping a user interface is, you can include the prospective user in the visuals. Just like Mystery Science Theatre, you can get reactions while showing what's going on on the screen.
It is not as simple as it looks - figuring out what to include in each frame, what dialogue might occur, and how to tell the story clearly requires a cinematic approach. It is almost more like developing a graphic novel than an interface design.
I often cartoon about people - and animals - interacting with technology. Now, I'm thinking that maybe these could be counted as user testing. That is, if you want to know how animals might use computers. Wave of the future, you know.