This is a really great blog CNN has set up about things being done to combat child sex trafficking around the world:
http://thecnnfreedomproject.blogs.cnn.com/
There's an estimated 1 million children in the US being used for prostitution, so it's a huge and hidden problem. One of the articles talks about how Hilton Hotels has recently pledged not to turn a blind eye to sex trafficking at its hotels around the world, using UN guidelines to determine when to act and when not to.