I also think this most recent ESC legislation that President Bush vetoed was preventing the use of already existing embryos that were frozen in the in vitro process. The parents who did not expect to use the embryos were going to give them for the research.
To my knowledge "fetal farming" does not exist, nor is there any plan to have such an operation. I think they were just planning ahead for that possibility.
Actually, in a not too long ago presentation by researchers from the research group in Worster, MASS, the presenter didn't even try to hide the fact that they are planning for moving from embryo cloning and harvesting to cloning and raising fetuses to a better age for tissue differentiation for harvesting. Harvard research is already implanting living embryos into extr corporeal uterine tissue and rasing them for a few days then destroying them. The Japanese are already keeping goat fetuses alive in artificial wombs for seventeen weeks, so other mammals are next in the experiements. I think I included that in the online book linked
HERE if you would like to dig it out of the approximately 100 pages of text.