Healthcare is one of the areas where open data will potentially take off soonest and have the biggest impact.
Collective intelligence. Think of how Wikipedia works, how Amazon harnesses user annotation on its site, the way photo-sharing sites like Flickr are bleeding out into other applications… We're entering an era in which software learns from its users and all of the users are connected.
Pursue something so important that even if you fail, the world is better off with you having tried.