Yes, there are both scientific and ethical hindrances concerning research in humans. (I will not comment on animals.)
A good starting point is a critical review of the then current International Society for Stem Cell Research (ISSCR) guidelines on egg providers by Francoise Baylis and Carolyn McLeod (2007) ('The stem cell debate continues: the buying and selling of eggs for research, 33 Journal of Medical Ethics 726-31).They assert that the ISSCR takes a prohibitive stance towards paying women already undergoing IVF (egg donors) but a permissive stance towards paying those whose eggs are collected outside treatment (egg providers). For the latter, payment is permitted provided there is no undue inducement. This practice, they assert, fails to recognise that for Third World women or poor women in First World, low levels of payment are sufficient to constitute inducement and possible exploitation..
Baylis and McLeod also raise issues of medical professionalism (e.g., the treating doctor shouldn't also be the lead researcher) and scientific issues concerning ovarian hyperstimulation syndrome in egg donors. I also discuss these and other issues in my article 'The lady vanishes: what's missing from the stem cell debate' (2006) 3 Journal of Bioethical Inquiry 43-54.
So, we have already constructed a technique to extract ES cells from human embryoes based on your papers. What about porcine's ES cells, have we sucessed to extract that?
Please read it and share it with everyone. It is talking about prosumer also for the first time in this book we talk about magic and its power in product design. It is talking also about future of consumers .I request you put the link of book on your page and your school website for your students.