In the world of venture capital, a success rate of 30 percent is considered a great track record. In the world of international development, critics hold up every misstep as proof that aid is like throwing money down a rat hole. When you're trying to do something as hard as fighting poverty and disease, you will never achieve anything meaningful if you're afraid to make mistakes.
While I applaud the intentions of the voluntourists of the world, I think it is important for them to remain grounded in reality. They need to be constantly cognizant of their privileged positions to be doing development work in the first place and the limitations of both their time commitments and outsider status.