This is a highly charged issue. I will do my very best to be neutral. Comments which are not, in my opinion, neutral will be ruthlessly moderated away.
Allen Murabayashi over at the photoshelter blog has a piece up, and there's a previous piece of some worth as well. While Allen himself seems to be trying to maintain distance, he's quoting a lot of people who are trotting out the same tired business about how "this is all new, and so much worse, and it's numbing us all" which has been something of a drumbeat, well, forever.
Images of extreme violence have been with us forever. I don't think there's any actual evidence that they numb us particularly, we're already numb. Things that happen to us are simply of a wildly different order than things that we see in pictures and videos. Also, the degree of sheer nastiness that was committed to the photograph in days of yore was vastly higher than now. Seriously. People were gleefully shooting shit that is now the material of nightmares, because in 1890 or whatever, it was pretty ordinary stuff. Susan Sontag went on at some length on these topics in Regarding the Pain of Others and it's a little surprising that Allen doesn't cite her.
Anyways, Sontag is definitely present, notably in the way that the various chunks of video, the various stills, are interpreted, presented, and discussed. Probably the only really new thing that's appeared recently is the cell phone video, which is different from what came before largely in that it leaves essentially everything open to interpretation. It's a moving set of indistinct blobs, and an inscrutable soundtrack. This leaves the field more open than ever for applying whatever narrative you like to it, and people do. They always did, but they spent a lot more time imagining what was outside the frame. With a cell phone video, you can imagine what's in the frame as well.
As always, though, the "photograph" (or video) lends a beautiful sense of certainty to it all. You can see it all so clearly, it's obvious. The people who disagree with you either have not seen the video or are insane partisans.
Police-worn body cameras are not going to change this. The may provide a better quality of video (it is inconceivable that it be worse), but I predict that we'll see the same incomprehensible videos. A mass of bodies, a frequently obstructed view, shouting, an occasional instant of clarity. A sound that is either a gunshot, a car door slamming, a someone tapping the camera, or any number of other things. Onto this mess will be projected whatever narrative the viewer favors, and the video will, again, constitute "proof."
Pictures of cops going about their business are, I believe, tremendously worthwhile, nonetheless. They have real evidentiary value, in reconstructing timelines and corroborating or refuting testimony. They do not, by themselves, provide any sort of useful narrative, but that's quite a different thing. Secondarily, but perhaps of greater long term importance, they present the police with the useful sensation of being observed.
Policing is the sort of job where, to be blunt, it's simply done better when it's being observed. Observation of the worker stifles creativity and damages morale, but for some jobs, it makes the quality of the work go up. And I want my policing to be done at the highest possible quality. Frankly, if it damages the morale of the police force, so be it. Media backlash and getting shot also damage morale, I expect, so maybe it'll be a wash in the long run.
So, while I approve of videoing the police at their business, I do not think, and neither should you, that we can expect to "learn what went down" from any such videos. The court system works vastly harder at this problem than the layperson, has far more machinery to apply to that problem, and does a fairly rotten job of it themselves. It is ludicrous to suppose that we can look at a video on youtube and "know" in any meaningful sense what happened. But gosh, it sure feels like we do!