Wolfgrrl-
I had the same question. I started doing some research and although I don’t think I nailed it 100%, I did come up with some interesting insights.
I could be wrong on all this, but being an ex-computer guy, I think at least some of it is more than coincidence.
It appears the spiders hitting the site are counted in the Visitors summary by Statpress. I turned off counting spiders in the statpress options and saw my Visitors count drop almost in half.
Also, I did a DNS lookup on the Top IP-Pageviews on the Details page. Many of those were hitting my site 100s of times per day and they were from other countries (that I don’t think care about Minnesota real estate). I put a deny from xx.xx.xx.xx in my .htaccess file to block those IP addresses. I assume they are some sort of spam or Splog servers.
Lastly, I took a hard look at the Statpress Spy page and realized that several of my pictures were being linked to by MySpace pages! I quickly renamed the files to break the links. Again, I think Statpress was counting those as users. Google only runs when a page is accessed.
Time will tell if these changes were actually the correct ones, but this is my $.02 on the issue.