Big Chris - if you have looked into this, and seen for yourself how against it a LOT of herpers are, why are you taking everything so personally when people are replying? You have started a discussion and people are going with what YOU are saying, and providing responses for that - if you don't like what you hear, think about it before you say something in the first place.
Please don't shun science and facts as "absurd" just because you don't have the understanding of the findings. People spend years of their lives researching different animals (not just reptiles) in order to learn about them, knowledge that can then be applied to keeping them in captivity. Think of it from a different perspective: people have researched into children, found out how they play and learn at different ages, discovered that they learn with their mouths for a long time - which is why toys are labelled with ages to prevent choking. Would it be okay to give a baby a toy with tiny parts that it COULD choke on, just because it would enjoy it? You can't guarantee it would choke, but there is a huge chance and has been discovered through RESEARCH. How about hamsters? They come from arid areas, they're not seen in water, but would it be okay to insist they swim in the bath just incase they enjoy it? Even though it is alien and no doubt stressful? All the behaviours you mentioned are competitive, and you are not trained or experienced enough to realise that, please let EXPERTS do the explaining.
I'm not trying to drag up an argument again, I just want you to embrace research and see why it is important. It is such a useful tool. As for a pet shop and a vet agreeing on co-habbing, I'm training to be a vet, and reptiles are generally not studied in depth in most universities. Not only that, but husbandry of any animal isn't a vet's strong point either. As for pet shops, quite a lot of them don't really know anything about reptiles.
Lastly, you said it's not common. How do you know? People who often co-hab are pet shops, for ease of "storage" until purchase. If a few of their snakes get eaten, no one finds out about it. They're not going to tell their customers about it are they? Regardless of all of this, I think the moral of the story is, if you love and appreciate your snakes, which you must do to spend so long discussing them on here, why would you put them at any risk at all?