They actually have an example for a regular blurred jpeg at the end. And yes, a camera shake may big difference to a regular blur, but then again, an actual regular blur (so an unfocused lens instead of a moving lens) is less often the problem.
Wow, I had meant to have another sentence saying that it is probably still possible based on the "blur" technique used. But... yeah, I clearly did not say that.
I would assume most of the time people "smudge" the data they want to be removed from a photo. Though, as stated, adding new information to the image has got to be the best way to do this. (a blackout.)