FYI. Recently saw a story on television about a guy who broke into his wife/girlfriend's email using a password she left on a little sheet of paper by her computer.
Bottom line: he was arrested and charged with some sort of computer hacking crime. He may end up going to jail for several years over this.
I didn't pay close attention to the story and I'm not clear on all the details. But, while it's certainly not illegal to read a forum. Apparently it's illegal to hack into or read someone else's email without their consent.