If you need evidence that social networks can save lives, have a look at PulsePoint, a crowdsourcing app for connecting cardiac arrest victims with assistance.
PulsePoint’s free app connects to local 911 call centers and alerts users when there is someone nearby in need of CPR. PulsePoint users get an alert the same time as local emergency responders. It also shows the location of the closest automatic defibrillator (if there is one nearby) as well as a reminder about how to do CPR, just in case the user has an adrenaline-induced brain-freeze.
This is remarkable.
I suspect that it should be easy to measure PulsePoint outcomes with those of non-crowdsourced patients. This might bridge the elusive gap between social networks and health outcomes.