I suspect that a good fraction of the so-called guests are web-crawling bots.
Your hunch is correct. I routinely run some of these IP addresses through a spam checker site (or several), and 95% of them are known spammers. You may have noticed, too, that we have a daily influx of "new members" (

) who have somehow managed to join, despite Rob's anti-spam registration procedures.
I think the problem people are having is most related to connection speed. When I'm in my house on wireless or at work with high-speed cable, there is no noticeable difference. But when I'm out in my man-cave-garage where I need to use dial-up, the slowness of page loading is very evident. Since the last images to appear before the page is finally complete are the social network icons, they are most likely the cause of the sluggishness. While I think change that brings in new members is good, it's not worth it if we lose long-time members in the process.
Others have mentioned this, too. I'm wondering if there is a way to keep the Facebook and Twitter functions, but (just thinking out loud) not having them on each post. They could be located on the formatting menu, and you'd have to say, enter the post number. That way, the icons would only show up once on each page.
--Bruce