Some practical issues:-
Quality control. How do you ensure that all the same regulations that apply to farm animals apply to humans?
Diseases. Unlike with animals, every disease that a human picks up is, indeed, transferrable to other humans. Anyone want to eat an AIDs-infected carcass? Thought not.
Body disposal. Most humans choose to be buried according to the rites of their religion. Even if they're not religious, most people who've thought about it at the very least make provisions for the disposal of their body. How many would tick the box marked 'eat me'? Very few, I suspect. So, how do you sell the concept to the general populace?
More on quality - unless you go round killing people at random, most dead humans tend to result from old age or accidents - so you've got a choice of really grim old meat or mangled/charred meat - neither of which is particularly palatable, even to a hardened 'foodie'.
My light-hearted take on the whole thing....
