All that power has to come from somewhere...

Here's a page that measures the environmental impact of cell phones. The stat I found most interesting was how much energy is wasted leaving a cell phone plugged in after it has fully charged.

Now for a potential solution.... a solar powered cell phone charger / supplemental battery system by Novothink. Now your phone can run (at least partially) on the sun. I've read the specs - for casual mobile phone use, you'd need around 2 hours a day of exposure to the bright sun to stay off the grid (3.5 hours on a cloudy day supposedly). I think we need another step in the evolution of the efficiency of solar cells for this to become completely practical, as I think it's more reasonable to charge a phone in the sun in 30 minutes.