On the other forum, I think the debate was over the degree to which the DM (I prefer the term "guide" in this case to distinguish a training situation) is responsible for the safety of an individual diver. So much of this forum and diving culture is centered on personal responsibility and so I am always surprised by the level to which we sometimes go to assign responsibility for safety to our guide. At the end of the day if you are injured or killed, it is little consolation that it was someone else's fault so my personal attitude is that the guide is there to show me the site and where the critters are hiding, but not for safety any more than an other non-buddy on the dive. This is especially true on a group dive. It is impossible for the guide to capably take the responsibility for everyone. To say otherwise is simply waiting for a bad outcome and hoping there is someone to blame.
If you hire a guide, then they are there to be your buddy, not a super-human savior. I think most of us agree that they have a heightened responsibility to you personally and the reality of it is that they are more likely to be capable of helping you in this case because they aren't being tasked with responsibility for another dozen or more people. I think this situation is not typically problematic and not the source of controversy that brought this subject up.
All of that said, the point that was made on the A&I forum that I thought was an excellent one, but that I've never seen done, is that dive ops should make it clear what the role of the guide is. This doesn't have to be a don't-expect-me-to-try-and-save-you talk, but put into a safety briefing concerning the importance of your buddy, it could be effective. The guide does not have to abdicate all responsibility (and shouldn't because they do have a responsibility -- I just choose not to rely on it), but they can easily articulate the reality of the situation. You need a buddy because if you get in trouble, I still have a dozen other people I have to deal with and as much as I may try and want to help you, there are times that I may not be able. The only solution is to push personal responsibility for safety as far as possible and I think there is a gap here. Dive ops should not be complicit in the delusion that the guide will save you and I think withholding this (obvious to some of us) information does just that. And I don't think this hurts business (can't believe this is a factor, but who knows) -- I go to Largo a lot and even without putting guides in the water business is booming. I think all this approach would do is to clarify something every certified diver should already know and it might make some people who would not otherwise, clearly buddy up.