Around May 5th 2010 Google updated their site design. Danny Sullivan of Search Engine Land has some excellent in-depth information about the changes. He discusses nearby filtering which is used so search results will favor local Websites.
In my SEO reasearch I noticed this update uses the Google Maps local results OneBox location to favor local results not only in the OneBox but also in the organic results. Once it is set it seems all search results favor that location. This means that everyone will be viewing somewhat different results depending on this setting.
This change might be great for a small business selling products at a bricks and mortar location. However, for sites that offer products and services that have a national or world-wide customer base this could seriously hurt their organic search traffic. Website owners and SEOs who don't realize this change has taken place might think their site is doing great, or poorly, in the SERPS depending on the Google Maps OneBox setting. Universal and Personalized search have been around for some time now. If this OneBox change remains, trying to get a page ranked for any keyword phrase will be more difficult.
Your comments on this subject are welcome.