One might wonder why when a user arrives at your site from Google that their query string is www.yoursitename.com ? I mean if they know your site URL why would they go to Google and query it? Good question fine reader. The answer is not some sort of insidious characterization of intelligence levels of Web users like some sort of Red State / Blue State voting pattern conspiracy, but instead a simple theory - Google is their home page.
Consider if Google is your home page that it will focus the search box immediately unlike other pages which will have the focus on the address bar. That little usability improvement called 'first field focus' causes a little hickup when the user meant to go directly to your site they take a brief sidetrip to Google to run the query. The likelihood of our theory being true is pretty great given that http://www.google.com/search?hl=en&q=www.port80software.com and other similar queries now produce a single answer from Google helping you get to your intended destination.
Of course if you don't buy our thinking you are more than welcome to continue to question the intelligence of all those users out there.