Consider this, we take an adult nucleus, and insert it into an embryonic cell. Why does it revert? We have ideas, but very little actual understanding. It was only several years ago now that we even discovered the existence of microRNAs, a fundamental nucleic acid that has ramifications that can far outstrip the effects of protein expression. I do this type of work, and it is humbling and bewildering, and not on a metaphysical level. There is a lot of shit going on in the cell that we just aren't yet privy to. But, heck, even what we do know can give us pause against cloning humans. These animals often suffer from shortened telomeres (repeating ends of their DNA), and this has been correlated to advanced declined in cloned animals. Basically we are sticking old DNA in a new embryo and running with that. Not good enough, IMHO. But, like I said, I do foresee a point in the not-too-distance future that these obstacles will be overcome, and I will be much more receptive to the idea. I'd just hesitate to ascribe too much of the hesitation to taboo. Some of the hesitation is scientifically-minded and based on evidence.