On the right side, click on your team of interest. This triggers a search for that team's hashtag. For example, clicking on the South African flag searches on #RSA. Searches are performed within a 12 mile radius of San Francisco, CA, and only for the date of the match clicked. Twitter's search API restricts searches on past dates to recent dates only; it seems 1 week is too far back to search.
If the user geotagged the tweet, it is plotted on a map with a flag indicating the team mentioned. If the user mentioned both teams, it's assumed there was no team preference for that match, and the first (home team) flag is plotted. If the user did not geotag the tweet, the script checks if the user manually entered coordinates or a description (such as SF or San Francisco) into the user profile location field.
If these fail, it's assumed there is no directly available location information and the tweet is not plotted on the map, but it is included in the tweets printed below the map.
This page was created on a whim using the Google Maps API, Twitter search API, jQuery, Sass, and Smultron. I'm not a developer so it took me a few hours. If you are and you peek at the source, you're likely to become a bit apalled. More information on how I did it is written in a blog post.