The ad in the back pages of the free Washington, D.C., news weekly was curious enough, warning women that they or their loved ones could suffer from debilitating diseases like Parkinson's or cancer and inviting them to let their eggs "be part of the cure." But it's had reverberations 2,500 miles away where a debate in California is raging over how scientists can acquire the human eggs critical to stem cell research -- specifically, whether it is ethical or even legal to pay women thousands of dollars to provide them. The ad in the Jan. 3 issue of The Washington...