A typical evolution talk doesn't stray into the field of ethics. Ethics, as a whole, is the domain of human decision making and action, whereas evolution is a natural process, and nature is nonethical. However, science has reached a point in which it is possible to elicit evolution. Researchers have successfully evolved bacteria and plants on far smaller time frames than in nature, and it won't be long before these same practices could potentially be used on humans.
In his evolution talk, Juan Enriquez asks whether engendering evolution in humans would be ethical or not. He first considers the current age of prosthesis. Up until recently, prosthetic limbs or organs were something that someone with a disability needed. However, modern technology has adapted prosthesis immensely -- hearing aids that provide preternatural hearing or bionics with quicker reaction times than even the sharpest human reflexes. No longer are prostheses a matter of need, but potentially a matter of want.
It doesn't take much imagination to extend this line of thinking to the manipulation of genes and cells. Enriquez urges that people think deeply about these enhancements before accepting them en masse.