Whether or not harm comes of it is kinda beside the point. The point is that if you've promised not to reveal information, you've promised not to reveal information. If you do so anyway, you're in the wrong.

If it's a whistleblower situation, breaking that promise can be justifiable, but leaks like this aren't that.

I mean it's just a right to privacy really, isn't it?

People have a right to privacy, corporations don't.

Legally speaking, they do. Not to the same degree as people, but still.