Make a difference, then a profit: building startups that do social good

A cursory glance through the top apps in the Apple App Store or Android Market reveal solutions to a variety of first world problems – from shopping dilemmas and cooking catastrophes to simply too much free time. But with so much technology out there to make our lives easier and more entertaining, what about some that address real problems, like a solution for world hunger, an app for purifying water, or a tool that gives a voice to those who have been silenced?