The Johns Hopkins Hospital recently changed a number of their old-fashioned, manually-controlled faucets for fancy new motion-sensitive ones that you didn't have to touch at all. They immediately saw a spike in Legionella - a potentially deadly kind of bacteria that can cause pneumonia. The hospital took samples of the water from 20 of the new taps and 20 of the old ones, and found that 50% of the touchless type had Legionella, where only 15% of the manual ones did.
They're not really sure why this increase has happened, but the standard disinfection methods for the faucets doesn't seem to work as well, possibly because the complex valve system of the new faucets gives more surface area for the bacteria to grow.
On the plus side, the electronic versions use less than half the water of the traditional ones.
Research presented at the annual meeting of the Society for Health Care Epidemiology