While in Granada, Nicaragua this past week, we met person after person who was there for altruism and volunteering. People from Liberia, America, Croatia, and other countries.
I believe some guilt comes into play when people get into third world countries, but adventure and altruism, along with boredom at home drive a fair amount of volunteer tourism.
Interestingly, some of the volunteer tourists seem to be participating in pedo-tourism as well there. So in this case, what is the driving factor? What a dichotomy.