From the WSJ:
Created to help the world's couch potatoes turn the tube on and off without having to make the arduous 2-meter journey to the TV set, the standby feature has spread to virtually every appliance in the home and office. Microwave ovens, cellphone chargers, DVD players, computer monitors and printers all silently consume power when they aren't in use.
The cumulative result is huge. A study by the European Commission found that Europeans waste €7 billion ($9 billion) a year paying for appliances in standby mode, which account for about 10% of total energy use. The drain can be higher. A study by the University of California, Berkeley, found that such snoozing machines consume as much as 26% of electricity used in gadget-stuffed homes in California.
Machines on standby are responsible for about 1% of the world's greenhouse-gas emissions, according to the International Energy Agency.
Governments have tried advertising campaigns to coax their citizens into unplugging cellphone chargers and turning off their TV sets at night, to little effect. Many new devices, such as Nintendo's Wii game console, lack an off switch. Users must unplug the devices to stop them from consuming power.