What is hidden in Caché?

In his recent Great Movies review of Michael Haneke's "Caché," Roger Ebert writes of a shot he believes may hold the key to the film's mystery:

How is it possible to watch a thriller intently two times and completely miss a smoking gun that's in full view? Yet I did. Only on my third trip through Michael Haneke's "Cache" did I consciously observe a shot which forced me to redefine the film. I was not alone. I haven't read all of the reviews of the film, but after seeing that shot I looked up a lot of them, and the shot is never referred to. For that matter, no one seems to point to a conclusion that it might suggest....

No, he's not talking about the final shot: "You will find it on the DVD, centering around 20:39," he says. "You tell me what it means. It's the smoking gun, but did it shoot anybody?"

Roger followed up with a blog post about the shot (which you don't want to know about if you haven't already seen the movie) and I offered a couple of comments: here and a follow-up here. Many interesting takes on the film can be found in these comments, which (as I write this) number more than 130. Critic Michael Mirasol, whom Roger quotes, thinks the stationary shot (#2 below, a reverse-angle of the film's opening shot, from Georges and Anne's bedroom, toward the street where the video camera is concealed) is from Pierrot's POV, and provides evidence that links him to the mysterious "Lost Highway"-esque surveillance videos. I don't see it that way, but here are the four shots in question (images from moving shots indicated with arrows):

1.

The postcard to Georges that Pierrot gives him in the car.

2.

Long, stationary shot from bedroom window, looking down at the street from which the movie's opening shot (top) was taken. Faint breathing, rustling heard on the soundtrack. This reverse-establishing shot serves as a necessary set-up for the double-shock of the next shot, another reminder not to take for granted what we think we see...

3.

POV shot (hand-held, not locked down like the previous shot). Sound continues from the shot before, and at first we think it is inside Georges and Anne's place, but it isn't. When the camera rounds the corner to the right, we see the boy and the blood. This is the first of several times in which Georges' memories begin seeping into the movie. The next time this happens -- a longer sequence, with Majid and the chickens -- it will be followed by a shot of Georges' waking up from a nightmare, retroactively placing these "flashbacks" in context. But at this point in the movie, we have no context for this image, which comes as a disorienting shock. Only later do we realize how it fits into the past shared by Georges and his childhood friend Majid, memories fraught with guilt, betrayal and denial.

4.

Georges and Pierrot returning to the car (the next morning?), parked on the street seen in shot #2 above. Notice how Pierrot is held in the background of the shot behind Georges -- and in the passenger seat mirror. (Composition and mise-en-scène create their own meaning, plant their own "clues," every bit as significant as plot, dialogue or character behavior.) The paper on the windshield could be another bloody drawing... but turns out to be an advertising circular.

So, to re-state what I said over at Roger's: I think shot #2 is meant to be a counterpart to the video shot that opened the film, but it's not a POV shot (too steady for that). It's basically a reverse-establishing shot (telling us it's now nighttime at home) that bridges the drawing of the blood-spitting boy (#1) and the memory/dream of the blood-spitting boy (#3). Shot #4 is reversing the movement from shot #1, as Georges takes Pierrot back to school again... where, in the movie's final shot, we may or may not notice him meeting up with Majid's son, indicating... what?

CONTINUED: Michael Haneke explains his methods here: The Haneke MacGuffins: What is the mystery?