Polonius's privacy problem

Is it ok to invade a fellow friends privacy when they seem deeply introuble. In Shakespears "Hamlet" this seems to be a big question for many. I believe that Polonius definately stepped over the line with this one but it was for a good reason. Obviously Hamlet is going through a horrible depression and its putting the lives of many close to him in jeopardy. Polonius needed to see what is going on in his head.