VeganEssentials, here's my thoughts on the B12 deficiency and why I don't like depending on supplements and why it will never 'catch' me.
By the way, I have always liked your posts (or the ones I can think of) and considered them to be independent and thoughtful opinions so I am glad we have the opportunity to discuss.
1. (A priori; cannot be scientifically proven; based on logic/observations/personal experience) I consider nature made us perfect. Nature made us vegans. Everything else is deviation from our natural environment. Carnivores exist, they have a place in this world, they are a part of the circle of life but we humans simply do not need to eat meat. Like pigs and many other animals, we have the opportunity to be omnivores but this is only a chance for us to survive in harsh conditions (scarcity of food). Harsh conditions are not our natural state of living but a deviation that humanity has been living in for the past several millenia (our perfect environment being something like Avatar).
2. As vegans and as beautiful beings we were designed to interact with our environment like all other beings. We have sight, taste, hearing, touch, etc - these are the guidelines that nature left us. When all these are in harmony, we also get what people call 'the 6th sense'.
3. When we deviate from our environment, we face the consequences.
4. B12 deficiency exists! B12 is produced by bacteria found in the small intestine and in the soil (among other places).
5. B12 deficiency is one of the natural consequences of us deviating from our natural environment. As Dr. Douglas Graham says, in nature we do not eat very clean food so B12 inevitably gets into our bodies. Also, in nature there are no pesticides and insecticides which kill the bacteria producing B12 in the soil. As Dr. McDougall (I think) said, B12 deficiency is the bad side of good hygiene.
6. Our bodies produce B12. Whether we can use it or not is debatable (Reading all the articles that 2097 posted is on my todo list. Thank you, 2097).
7. I interact with the environment a lot, for example I happen to eat wild berries from time to time (like, really wild ones, from the mountains) and I do not depend on the supermarket for food. Therefore I am confident I will not get any B12 deficiency (which I have not experienced so far).
8. B12 deficiency is common among meat eaters (omnivores) as well.
9. I am quite sure there are many other negative effects (may be not even diagnosed yet) associated with our deviation from our natural state. Therefore, as hard as it is, I try to keep as close as possible to this natural state. I am fully aware that I lack many things and I cannot care about them all but B12 is certainly not one of them (well a V6 still is
So, yes, if someone wants to be on the safe side and take supplements, sure! I myself am confident that I do not need them. Selling supplements is among my activities (Yeah, I do many things and they earn some money which allow me to practice the 80/10/10 from time to time) and I will say once again that I have learned not to underestimate the benefits associated with them and not to overestimate the scare associated with not taking them (i.e. that's an aftermarket paranoia which the supplement/pharmaceutical companies don't even cause directly. Just people fall for it and the companies don't mind it, except for swine flu hoaxes and the likes of them).
There's a natural explanation of everything. For example, I once wanted to increase my zinc consumption. Pumpkin seeds are very rich in zinc. However, most of the soil in Turkey and China is very poor in zinc. If I did not know that second part, I'd buy Turkish pumpkin seeds (because they are on the market), get no effect and then fall into a cognitive dissonance blaming who knows what.
The 80/10/10 diet gives a logical explanation of B12 deficiency and a good way of overwhelming it. If some people don't like it, good, it's a book, not something compulsory anyway. And critical thinking is a sign of free will anyway (assuming that free will is something good