Well, aside from the ridiculous money involved with this procedure (as noted in the link), what are the chances of success realistically? Dogs have over 13 different blood groups with 8 DEA types, which is way more complex matching than a cat or human. A sibling would be the best chance, but I see it as slim and desperate. If all the planets and stars were aligned so to speak, I really don't see a problem with performing the procedure, though.