This is going to be helpful mainly in macro marketing campaigns where you cant control where the customer calls from. Think adwords, website, newspaper, etc.
You take the information and download into an excel sheet (no formulas needed). Just use top bar to list name,address, city, state, zip, phone, or whatever else. Then save in csv. and go to google mymaps to upload.
You can upload the info and see on a map where clusters are occurring.
So for example you can upload all your internet customers or all your tile customers, adwords, etc and see if anything interesting happens. The cool thing is you can layer it so each one is colored differently. Its really unlimited….
Here is a link of a small one i did for carpet retailers to see what i mean. Cant really see anything specific i know but try it with hundreds or thousands and you will definitely see clusters in some cases. Which may give you an idea of where to invest next.