If the admin hasn't set either constant im_screenname or im_password, when users goto /my/messages they will see
From this page you can configure various messages that Slashgeo can optionally send to you. The primary options are No Messages (Disabled), E-mail, Web, AIM, and Mobile Text. Not all options are available for all message types. Web messages will be deleted after 14 days. If you plan on receiving AIM messages, please add to your buddylist.
Not only that, but the pulldowns for the options for each message channel seem to contain the options for AIM, too.
This also shows itself to happen on a default, brand new slash-site install.
