Not to beat a dead horse, but one of the most important skill sets that a course like Fundies beats into the student is being a good buddy and approaching the dive from a team mentality.
Shall I paraphrase John Wayne - Diving can be tough. Diving is tougher if you're stupid.
The thing I'm not seeing in anyone's posts is what they think it means to be a good buddy. Within a foot of each other? What if you are taking a picture of your buddy, going for a wide angle shot, and then they have the OOA emergency (although maybe you'll get a great 'candid' shot of the OOA signal)? You're not exactly going to be holding hands at that point (something I've seen from some married buddy pairs, even with reasonable viz).
When I dive as an instructor, I have to keep a close handle on all of the students. Even that can be tough, which is why you want an assistant with more than 2 divers - newbies tend to have problems, and if you have to go to the surface, you can't leave a non-certified diver at the bottom alone. Even then, I have had the oppurtunity to take a camera down with me in a BCD pocket, and pull it out on the tours (oddly, forcing me to watch my own students very closely because I have to be close to take good pictures of them). With newbies, I'm staying within 5 feet of them, and I'm looking for them every few seconds. It takes away from my ability to find things for them on a tour, but that's not the point with an Openwater class, safety is. If you're diving with a buddy where you've been with them for 100+ dives, you know their level, and, most importantly, you don't have a huge liability based on teaching them, its a bit different. Personally, I view the first rule of diving as being the first rule of first aid - don't make yourself an additional problem. If you know your buddy is a responsible diver, you can be a little more slack, because you know you are being a safe diver, and you know your buddy is a safe diver. If you don't know your buddy, you have to assume the worst, because the reality is that not all instruction is equal. I have had numerous AOW dives where I didn't bring my 10+ pound Patima aluminum housing on a deep dive, in part becauyse I didn't teach all of the divers, and in part because it would get in the way and potentially prevent me from stopping a panicking diver from going to the surface. I am willing to bring a small PnS that I can stuff into a BCD pocket on those kind of dives, although it won't come out until I decide I'm in a "safe" water level, and even then its tethered so I can just let it go.
Remember that if you have a problem, you have to evaluate if your buddy sees you, if you're close enough to reach your buddy safely versus going to the surface, and whether you need to do a safety stop. The reverse is true, too. If you or your buddy has a problem, and you're close enough, you swim over, grab and shake your buddy to get their attention, and do what is needed. Team diving is largely an illusion. In general, my opinion is that if you're underwater, you should act as if you are on your own, even if you have a good buddy. If your buddy can help you in an emergency, more power to you. But the goal is to make sure the emergency doesn't happen, not to assume that your buddy is going to be there to help you. After all, if you have a problem with an unknown or inexperianced buddy, you have no guarantee that they are competent enough to help you, certification level not withstanding. You also have no guarantee that they see you, or that they won't just lock up in the face of the emergency. Ever seen a person forget about their skills in a real out of air emergency? I have, I had to take control. Ever have to stop a panicking diver from rushing to the surface because they snorted some water? I have. Ever need to tell a buddy that they are low on air and need to go to the surface right frickin' now? I have. None of those divers had a camera. The camera is irrelevant to this. Watch your own air, keep track of time, watch your bouyancy, don't harass the wildlife, and make sure you keep control of your own emotions so you don't panic. Yes, you should stay close to your buddy so you can help them, and keep good visual contact so you can see them signal. Ideally, your buddy is close so you can potentially take pictures of each other, or you can see the same things on your dive. But when you have close to 100' of viz, its pretty easy to get 20+ feet apart, more than enough that you are really on your own, even though you have the sense of being in a team. I wouldn't do that with students, but when I dive with another buddy who's an instructor himself, yeah, its happened (and then some). Diving is about seeing the underwater life, not constantly watching your buddy. You will *always* have moments where you're not watching your buddy, irregardless of the camera. Bottom line - its not the camera that makes you an irresponsible diver.