People who can't keep their bloody mouths shut!

You tell someone something you don't want anyone else to know, either for a while or forever, and two days later somebody else mentions it to you. After you specifically asked them not to tell anyone, they couldn't wait to shoot their mouth off.

Same person says to me, "Don't tell so-and-so that I told you this, because I am not supposed to tell anyone." Then just stop talking! I don't want to know what so-and-so told you, because she is my friend, and if she wants me to know, she will tell me herself. Just STFU!