This article in the NY Times fits nicely with my belief that carbon offsets are bullshit.
"The carbon offset has become this magic pill, a kind of get-out-of-jail-free card," Justin Francis, the managing director of Responsible Travel, one of the world's largest green travel companies to embrace environmental sustainability, said in an interview. "It's seductive to the consumer who says, 'It's $4 and I'm carbon-neutral, so I can fly all I want.'" Offsets, he argues, are distracting people from making more significant behavioral changes, like flying less.
(via @daveg)