I wonder to what extent it sould be possible to allow for system messages, to be seen by the person the next time they refresh... This would be more like a slow im, with no history being kept, but rather an informal communication. This way, next to the anon's IP, there could be a "send text message" which would appear the next time the user requested a W page.
We already have it: Edit the User_talk page of a user, even one only known by an IP address; the message "You have new messages" will appear on their screen until they follow the link. It is indeed very encouraging as a new user (I must start doing it more myself...) :)