I was under the impression that anything not human, and nutritious was fair game. A better question than the one you pose, is "what makes something not ok?"
Is it morality? Religion? Empathy towards potential living food stuffs? Guilt?
Humans can ONLY eat things from living sources (other than trace minerals of course). Our nutrition comes from living things. You can survive on plants but what makes it ok to eat plants and not animals? And how would you feel about things that fall in between? Corals, Jellyfish, Insects etc? Where do living things get advanced enough that it is not ok?
And back to the point, WHY is it not ok? Because of the empathy again? Perceived emotions of our living food stuffs?
If we genetically engineered cattle and pigs with no brains (or at least no conciousness) would it be ok to eat them? What about simple lab grown tissue?
[ame="http://www.youtube.com/watch?v=C1nxaQhsaaw"]A
pig that wants to be eaten - YouTube[/ame]