I've wanted to write this entry for a long time but I keep forgetting.
So as far as I can tell, there are two reasons why you'd want a water-faucet that automatically turns on when you move your hands close to it (like in newer public restrooms):
1) So you don't have to touch the faucets that other people have touched after using the toilet,
2) So people don't waste water by accidentally (or lazily) leaving the water on.
When I first went to the public restrooms near work I got all pissed off because the water wouldn't turn on. I looked helplessly to the janitor, who looked at me like I was an idiot and then looked towards the ground.
The restroom sinks here (not all, but some) have foot pedals. That's such an awesome idea. You walk up to the sink and just press your foot down on the pedal. You don't have to touch anything with your hands. And when you're done, the water turns off.
A low cost alternative to IR sensors (that often break) on sinks.