The problem is not that 3rd person needs to be mentioned, it is that using shaky cam is like going from 3rd person to 1st person then back to 3rd person.
Yup.
In a book I would find it confusing if the narrative kept jumping between 1st and 3rd person without a justification.
I like tricks like that. Then again, when it comes to art, I freely admit I'm a sucker for tricks. Or rather, I view art as a bundle of tricks that produces profound responses when done right.
Its not that it can't be done, but when it is, it is mostly by stating some means like a diary entry or 3rd person omniscient stating that this is what is going on inside some person's head.
The most common form of this is the free indirect style I mentioned, when there's deliberate confusion between
who is speaking; the 3rd person narrator or the character?
Consider the difference between:
Marie left without saying another word. "How can she be so cold?" said John to the empty room.
and...
Marie left without saying another word. How can she be so cold? The room was empty.
The first example is strictly 3rd person. In the second we start in the 3rd, slide into 1st, then back to 3rd. Happens all the time. A good chunk of the 3rd person novels since Flaubert (who's usually credited with inventing this trick) do this.
Whether something like this, say shaky-cam, becomes a lasting
film technique is anybody's guess.
(sorry for the tangent... I've been thinking about criticism lately, thanks to a great --and short!-- book called [ame=http://www.amazon.com/How-Fiction-Works-James-Wood/dp/0374173400]How Fiction Works[/ame])