Location's Fourth Dimension

While I was prepping for the Minnesota State Fair edition of the Foursquare Traffic Report, it became apparent that a fourth dimension is noticeably missing from the current discussion about location.
Those of us who work with location-based data know what a pain it is to define where something is. We start with coordinates on the globe, a single point on a quasi two-dimensional plane. From there we look at area, but is that enough? Do we define the Minnesota State Fairgrounds as a single instance of coordinates? What about locations that are within the boundaries of the grounds?

Over the course of the Minnesota State Fair There were over 200 unique venues used within the Minnesota State Fairgrounds. Only 12 were duplicates, and nearly half of the checkins came from a single venue, the 2010 Minnesota State Fair. 

The 2010 Fair itself is a more popular venue than the fairgrounds. How often does when trump where?  If someone checks in from Austin, TX the second week of March, chances are they're at South by Southwest. Which of the expansive list of venues are they going to use? I'm willing to bet that a popular new venue will show up in early March called 'SXSW 2011'. 

As more and more people use location-based services we'll see more 'temporary venues' based around events. Right now Foursquare has pages for venue owners. What happens when several 'temporary venues' exist within a larger venue? Does this change the way venue administrators look at managing their traffic data?