Hi Wes,
People keep on saying that google will penalise for duplicate content, but google has quite intelligent spider and it never creates any problem for the main
website hosting. Almost every
website hosting is crawled by www as well as without
www., but google gives first preference to the
website hosting which has more backlinks and previous index record in google cache.
Google will either not display content of your addon domains in search results, or it will give them low priority in comparison to the main
website hosting which has more backlinks and old cache record.