I see this subject as a double-edged sword. It is neither a good thing nor a bad thing, but rather it is both all in one.
On the one hand, the inclusion of CCTV in the flight deck does have some rather obvious investigative benefits when combined with the FDR and CVR data. In the case of the Air India accident, it could clearly indicate whether the start levers were actuated by man or machine. In the instance of the helicopter accident described in post 36, it's clear we would not have known about the accident sequence without the video. When I was much younger I was part of the company response to an internal accident where both pilots were killed. Having cockpit video would have told us a lot given the CVR transcript that we were provided indicated both pilots were making PF and PM calls, leading both the company and the government investigative unit to question who was flying the aircraft. So yes, there is an upside to accident and incident investigation. But that's the extent of it. To those saying it will act as a deterrence in the long run, I would point out that hypothesis has not borne out for FDR and CVR. There are still pilot suicides or pilots mishandling airplanes that disproves the deterrence argument.
Without the corroboration of FDR or CVR data to confirm the movement of a switch or lever, CCTV becomes an unreliable witness. Consider the case of engine anti-ice as a basic example. Approaching a cloud I may move my hand up to the igniters with the intent to move them to continuous, but perhaps the other pilot doesn't call for it, I see that the OAT is actually above the icing temperature, or the cloud layer is thin enough that I wouldn't even get up to the engine anti-ice switches before I'd be turning it all off again. All the video would show is that my hand moved up, stayed a bit, then came back down. It doesn't show my motivations for doing or not doing that thing and without the FDR to confirm the movement or lack of movement of the switch, the video doesn't tell you anything other than it was me. Suppose we have an Air India situation where there is loss of life. Just as I take my hand off the thrust levers with the V1 call a start lever is moved to the cutoff position. Unless the CCTV has another angle that can conclusively say that my hand touched the switch, you have coincidental movement of hand and switch. The video cannot necessarily corroborate that I touched the switch - unless of course it was a very deliberate movement. This is why I italicized "could" in an earlier paragraph. The CCTV can only tell you about the most deliberate of actions. One needs only look to professional sports to see how different people can interpret a situation: did the ball made it into a fielder's glove before the runner's foot made contact with a bag, or did the puck completely cross the goal line before the timer ran out. In these cases it is very clear the motivations of the individuals - one is trying to stop a run, the other is trying to acquire one. The same cannot always be said for workplace video.
Of course, that's not how the involved companies will view it. The airline, its insurance company, the manufacturer, and even the regulator will see the pilots movements not as a way of telling the truth, but as a way of getting out of the lawsuits. They will slow the video down and examine each frame for a way to show just how deliberate the pilots actions (or inactions) were. What could be an unconscious or routine movement made by the pilot will be seen as deliberate and against the movements of other pilots. Each company has their own motivations, and some will be more reputable than others. But make no mistake, one CCTV is included in an accident report, the lawyers will make damned sure to point the finger at the pilot.
As a result, if there is to be CCTV in the flight deck, and I believe that ultimately there will be, there must be protections for the pilots - whether they survive or not. At the moment, pilots do not have any sort of malpractice insurance. But you can bet that as soon as the first pilot is disciplined or charged because of video evidence, that form of insurance will become the standard. The pilot unions will call for that to be a part of the professional compensation, much as paid pilot medicals are the standard here in North America. I'm not sure what malpractice insurance runs for doctors, but the end result will be higher airfares. You'll have far more diversions and cancellations as pilots become less and less willing to apply their professional knowledge and experience because of how that could look on video, especially knowing that video could make it onto a social network one day. And what happens to that pilots career? I do not believe that the vast majority of accidents or incidents are caused by ill-intentioned people. Rather, I believe that most accidents and incidents occur to well-meaning pilots who zigged when they should have zagged. Before there was a sense of anonymity - you knew the experience of the pilot, but often not their name. You could read a transcript of what they said, but you didn't know who it was. Now you potentially have a face that is easily searched during a job interview or just as a curious individual. Now instead of being clear of an accident or incident after 5 or 10 years, this follows you for life, should you be apparently unlucky to survive!
In my country the most violent offenders get off in 25 years. Here we are potentially talking about an honest-to-god life time sentence. For what is almost always a mistake. I'm not sold that the investigative upsides are balanced by the loss to an individual's ongoing right to forgive and forget their mistakes.