It's not how big the voltage, it's the flurrent of the current. If you know what I'm sayin'.
I really really hope this actually works and not just someone trying to make a clever video based on what's happening in the Middle East.
From the Youtube description:
If you don't have electricity: Get two batteries and dunk them in the cup of water for 1 or 1 1/2 hours and then link the mobile phone with USB cable to the water! Great improvised technique for those traveling through revolution areas, or maybe just backpacking somewhere and you don't have electricity.