In my journalism law class, the professor [an attorney herself] told us of a story about a parent eavesdropping on her mid-teen daughter who was arranging a rendevous with a middle-aged man. The pedophile did get busted, but he subsequently filed a complaint against the parent for wiretapping, resulting in a conviction for the parent as well.
Needless to say, this story created considerable uproar in the class. I'll see if I can find it...