It looks like the Facebook "Like" buttons are registering as guest users rather than... something else. I have "like" buttons on the top and bottom of every single post so anytime a real user is visiting one of those pages, I'm actually seeing three user entries for that page, not one.
The buttons are generated by the WP Like plug-in but I don't believe how they're inserted on the page would make a difference. Let me know if you need any other information tho.