Demand. Supply. That good stuff:
Most volunteers choose to work with Cambodian children, usually by teaching English in orphanages. Be aware, though, that these Cambodian orphanages exist only to cater to foreign tourists. In fact, the vast majority of children who are placed in orphanages in Cambodia are not orphans and have at least one living parent. But demand from foreign tourists to visit Cambodian orphanages and work with Cambodian children is so high that parents are often offered powerful financial incentives to place their children in these so-called orphanages, or are promised that they will be provided with a great education, which is often not the case.
I suppose the best thing you can say about this is that being put in a show home and petted over by dipsticks isn't the worst form of exploitation the children might otherwise have to endure (assuming no visitors surnamed Savile). But how would an economist categorise this? The brainless compassion sector?