I think the key principle that underlies economics is that "individual incentives matter". Add some self interest (envy, greed), and look at the implications. I wouldn't think this way if I didn't think it worked.
I just lost 18 pounds via Stickk.com, a website that encourages weight loss and really any goal. It was founded by an economist based on the idea that incentives matter. I have wanted to lose some extra middle aged blubber for a while, but at the margin I had no real motivation (putting socks in the hamper would help my sex life more than buff abs). I knew I needed some outside force, so I created a contract at Stickk such that I had to lose 2lbs every week for 9 weeks or I would pay $50 for each violation to a charity that supported things I did not like (the anti-charity option).
The goal was cumulative, so basically my target weight goals were 231 lbs, 229, 227 etc. I gave them my credit card, and I had to report my weekly weight, and get a referee of my choosing to validate my progress. I chose a colleague at work, who would look at me on a scale I brought in. One could cheat the system, but when you involve another person, it's less likely. As an economist, I liked the idea: just give the incentive, make it strong, and let me figure how to get there. The algorithm is thus greatly simplified compared to Weight Watcher plans that suggest counting calories.
I only wish the website didn't try to do so much, classic feature creep. It seems to want to be a Facebook, allowing me to write commitment contracts on anything all while keeping up to date on my progress with pictures, etc.