Yes, have integrated google maps in this manner.
It's fairly involved however. You need to assign geodata to each of your customers (lat and lon), by making calls to the googlemap api.
You will either need to do this when they register or have a script do this later on.
Then another script to generate the google markers from the data and to load them into a map.
More ideas here
http://code.google.com/apis/maps/articles/phpsqlajax.html
We offer professional services if you are looking to outsource the coding of such a project.
Good luck,
Rubyaryat
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4.2.3 gold [Unix]