I thought that you can only access peoples facebook sites if you are in their network (is only Cardiff University students can see mine) unless you ask to be added as a friend so therefore you wouldn't be able to use this to look at.
Also surely what people do outside camp is their own business. It is how they behave at camp and around the campers that matters. So they may get drunk occasionally and the incriminating photos put on their sites but that has no bearing on whether not this affects their ability to work at camp.
I know someone that is a real goth with loads of tattoos and piercings and many people would cross the street if they saw her coming but she is also the most fantastic latin dancer and when she is in her dress and out on the floor she is a totally different person.
I would only consider using it against someone if they did something as bad as openly discussing the fact that they deal drugs or have thoughts that they shouldn't about young children- really bad stuff.