By Shannon Brownlee and Joe Colucci

When most of us think about Facebook, the first phrase that comes to mind probably isn’t “good Samaritan.”  Facebook is an easy way to keep in touch with friends, and it can be a gigantic time-suck, for sure, but last week the site did something that could truly benefit a lot of people. On May 1, Facebook launched an initiative to encourage users to become organ donors, and within 24 hours there had been a spike in the number of people volunteering their body parts for the good of others.

California’s registry saw almost two months’ worth of people sign up within the first day after the Facebook put up the feature.

Organ transplantation is one of the miracles of modern medicine, but there simply aren’t enough organs to go around for all the patients who need them. According to the United Network for Organ Sharing (UNOS), there are 72,900 people on active lists waiting for an organ. Compare that number to the 2,263 transplants that took place between January 2011 – 2012. Last year, more than 6,000 people died waiting for an organ.Obviously, increasing the number of organ donors could have a huge impact on the number of transplants – and on the lives of thousands of people.

Why don’t more people become donors? Some object on religious grounds, but the biggest obstacle is inertia. Most of us who sign up to be organ donors (I’m one of them) do so when we renew our driver’s license, by checking a box on a form saying we want to donate our organs. If you don’t mark the form, it’s assumed you don’t want to donate. Most people only encounter this choice every few years, when their driver’s license is up for renewal, and it’s hard to think about such a decision while standing at a Department of Motor Vehicles counter.

Some countries, such as Spain, Australia and Germany, have opt-out systems. It’s assumed that you are willing to donate unless you’ve said you prefer not to. Rates of donation in those countries are sometimes higher than in the US, although some presumed-consent countries have much lower rates. (Factors other than the number of donors, like the availability of surgical facilities and transplant surgeons, can affect the number of actual transplants in different countries.)

Another way to get more people to donate would be a “mandated choice.” This idea was proposed by behavioral economist Richard Thaler, in his book Nudge: Improving Decisions About Health, Wealth, and Happiness (with Cass Sunstein). Instead of a form that you can simply leave empty if you don’t know whether you want to donate, you have to choose between “yes” and “no.” There’s psychological evidence that even having to make that choice could get more people to think about their preferences and choose to donate. Israel has yet another incentive to get people to donate: those who are registered as donors get priority if they later need an organ themselves. Facebook’s effort depends on another psychological effect, the power of social persuasion. If your friends are all donors, maybe you should sign up, too.

Whether or not Facebook’s initiative will have a sustained effect on the number of available organs remains to be seen, but there’s a side to this issue that deserves at least a mention. Organ transplants are expensive. The surgery itself can cost as much as a million dollars, and that’s not including the drugs and other care transplant patients require for the rest of their lives. Granted, that’s money well spent in terms of lives saved. But imagine if there were enough organs for every person who needed one. We’d have to find more than $100 billion a year in addition to what we’re already paying for health care.

I’m not suggesting more organ donation is a bad idea, or that we shouldn’t do more transplants. Just the opposite. It would be money well spent. It’s also yet another reason to weed out the trillions of dollars we are on track to waste over the next decade on health care that doesn’t help patients or improve lives.

Joe Colucci is a research associate at the Health Policy Program of the New America Foundation. Shannon Brownlee, MS, is a nationally recognized award-winning journalist and author who has written for the New York Times Magazine, The New Republic, British Medical Journal and The Huffington Post, among many others. The post first appeared on the New America Foundation’s blog.