I just watched the 10 minute video at the Carrotmob website and I was truly impressed at the creativity of this crowdsourcing effort. What do they do? Well, it's a mouthful, but here goes. Carrotmob organizes a swarm of consumers on some random morning to go shopping at a store that has agreed to put a specified portion of every purchase towards becoming a more environmentally-friendly store ( 22% of revenues towards greening the store in this case). Carrotmobbers purchased about $9k worth of product, enabling the participating business to totally redo their lighting system and make some upgrades to their refrigeration units. As well, the carrotmobbers donated 366 pounds of food to the SF Food Bank.
This is an interesting concept, it would be nice to see it fly.