Some can do it with Hardcode tracking as well via an browser app (Toolbar) or even an small background running application that quaries a server on the net holding a database of link string variables.
www.urlsite.com/TourID?ID=XXX&index.php
Bing swap...
Before the viewer even see's the tour he just clicked.
The stuff is not rocket science, it is tricky theoretically but really nothing will stop a starving russian coder.