[0]: http://www.hopkinsmedicine.org/news/media/releases/latest_ha...
"While the precise reasons for the higher bacterial growth in the electronic faucets still need clarification, the researchers say it appears that standard hospital water disinfection methods, which complement treatments by public utilities, did not work well on the complex valve components of the newer faucets. They suspect that the valves simply offer additional surfaces for bacteria to become trapped and grow."
One of the things that surprised during my time going to school there was that even buildings less than a year old would have taps with standard levers. I guess they took their own findings to heart.