I am a guest on here a lot of times. I will read the topics and when I see one I want to repley to I will log on. I don't always log on because I just do a quick look, and am going to get right off anyways. (or I am just one big lurker) ;)
I think too, a lot of 'guests' on this site could just be people that are looking for puppies, so they are cruising through the ads. Or they can even be breeders looking at their ads, and that could be the reason for all the guests. Some may not even know there is a forum.