This one's very interesting. Moods is vulnerable to the typical problem that we've seen in the past. Mainly, viewing a non-friend's mood history. In order to check out someone's history, simply alter the following url.
Obviously substituting the person's id for the uid variable.
Now, here's the twist with this application. It doesn't even check to ensure that you are trying to set YOUR OWN MOOD! Yes, you can update someone's mood for them. Simply go to http://apps.facebook.com/emoting/ and copy the link to Update My Mood. It'll look something like the following. Now just substitute the proper ID for fb_sig_user.