SecTheory published a paper by Robert "RSnake" Hansen about Browser Power Consumption. Dan Goodin reports about it under the rather funny title Study spanks Adobe Flash for abuses of power (ehy Dan, why just Adobe? what about Microsoft and Sun?). PC World has an article as well, interviewing a Pacific Gas and Electric representative.
Of course it's just a drop in the ocean, but I like to believe I'm helping Gaia a bit and enabling others to do the same :)
Commenter Arthur reminded me that, even if you didn't give a damn about environment health, as a mobile user you surely value your battery life and you've got yet another good reason for using NoScript. And did I mention you can use NoScript on the Fennec mobile browser now?