It's a lot more efficient to make a couple Google searches than to drive to the library.
It's a lot more efficient to buy something on Amazon and have it delivered by UPS, which can combine trips like crazy, than to drive to the store--or possibly several stores--to buy it.
It's a lot more efficient that I used Campfire as an integral part of working remotely last summer rather than if I had had to fly across the country for the job.
Sure, it is still important to reduce energy consumption, and lots of computing doesn't directly replace more energy-intensive tasks (sending a tweet rather than ... driving to all of my friends' houses to tell them a very short message and then leave?), but computing has lead to lots of gains.
There'd be much less remote hiring without hi-tech options, too.
What about all of the energy savings that computers bring us, Greenpeace?
If Greenpeace and the rest of their ilk care enough, they should lead by example - announce that they'll no longer use cars, telephones, computers, heaters, air conditioners, or anything that was made by a process that also created pollution. No email, no internet, nothing more than riding on horseback to drop a letter made on hand made paper off. I think that would be good for them as an organization and good for the rest of the world.
And somewhat less abstract: if someone argues in favor of a smaller government, they are not automatically anarchists that think there shouldn't be a government at all. Painting a world without a military and challenging them to go live in that world is not a proper counterargument.
But when one entity is running all the powerful computers, then shaving off a few watts makes someone a lot of money. So they'll do it.
As for the green issue... I think it's good that Greenpeace is reminding folks that just reducing the number of watts you use isn't enough. You need to get those watts from something renewable or clean; not coal. Otherwise you're still destroying the Earth... just not quite as quickly.
The posts below bring out good points. Energy use is not in itself evil. One must consider what good was done with the energy. Watt-for-watt, those server farms are doing a huge amount of work on behalf of people.