Here is a Venn Diagram made with Twitter Venn that shows the relative frequency of tweets made about the recent deaths of three celebrities - Michael Jackson, Farrah Fawcett, and Ed McMahon. This analysis was done around 7am EST today and the absolute numbers for tweets/day will certainly increase as more people in the US come online. I expect the proportions among the various combination regions to stay roughly the same.
A couple of points of interest:
To explore the data using the interactive application click on the image below or this link: Twitter Venn for #michaeljackson, #farrahfawcett, and #edmcmahon.