Conservation while I travel?

Shortly after booking a hotel room through Travelocity, I received an email with "some goodies for your upcoming trip" according to the message. There was an ad from Blockbuster Video, but the one that caught my eye read, "Offset Your Trip's Carbon Emissions -- Effectively offset the negative environmental impact of your entire trip here. Go without guilt - Go Zero!" and linked me to a travelocity page that described how, for a small donation to The Conservation Fund, I could wipe out the damage my travel was going to do to the earth. The landing page assures me:

"A contribution of:

• $10 offsets an average trip including air travel, a one-night hotel stay, and rental car for one person
• $25 negates air travel, four-night hotel stay, and rental car for two people
• $40 equalizes the effects of air travel, four-night hotel stay, and rental car for four people"

This reminds be a bit of 16th Century indulgences offered by the Roman Catholic Church, but nevertheless, what I love about this is the clever tie-in of the offer with travel confirmations. I'd love to see travel confirmations for trips to developing nations tied to appeals from international development agencies. Perhaps it would be even more successful if it were tied to the email Travelocity sends after such a trip.

If you know how this offer is working, or know of any similar offers, please let us know.