The Cambodia Daily recently had an excellent article on the problem of orphans being exploited in for-profit orphanages. Unfortunately you have to pay to read the whole thing.  (The Cambodia Daily's webpage is frustrating.  I wish they'd figure out what they are doing.)
But the Age has an article on the same subject.
Stealing a generation: Cambodia's unfolding tragedy

NGOs in Cambodia for years now have been trying to tell people not to visit or support privately owned orphanages, but unfortunately their is a slow learning curve in Cambodia,  (I didn't know anything when I first got of the plane either) and by the time backpackers realize what's going on the damage has been done and they're ready for the next batch of fresh faces off the plane.
So spread the word--if you or someone you know is visiting Southeast Asia, don't visit the orphanages.