The March 29 issue of New England Journal of Medicine has an interesting article on The Egg Trade — Making Sense of the Market for Human Oocytes. N Engl J Med 2007;356(13):1289-91. (subscription only).
There's also a supplemental interview (free) on the topic with Emily Galpern, project director on reproductive health and human rights for the Center for Genetics and Society in Oakland, California and Debora Spar, a professor of business administration at Harvard Business School, Boston. http://content.nejm.org/cgi/content/full/356/13/1289/DC1
The key question here is whether it's ethical to pay women for eggs that will be used for reproductive purposes but not pay them for eggs used in stem cell research - creating two different economic markets in the process, each with very different incentives and outcomes. See what you think!