Mike the majority of those guests lately have been the google robots that search through sites, for some reason they have been all over the forum lately. They must be doing a huge sweep of it or something. I really dont' know where or what they are doing, but they have been doing it for a while now.
Guests don't have the opportunity to chat, otherwise I would be afraid of it being abused. If you have to be logged in I can ban those that abuse the chat room.