I appears after a few minutes of looking online that Plat 5 star status is only for a very, very few people out there. It is basically someone who either lives at a high end Marriott property, a person on the Board of Directors of Marriott or some other influential person (like Mitt Romney). It appears the designation is given by Mr. Marriott personally.
Hey medsales, I did some research on this and our team confirmed that the Platinum Five Star is not a status members can earn. It is a VIP status. Unfortunately our team doesn't have any additional information.
Continental Airlines used to have a double secret probation area called CO STAR which was given to certain very very high end frequent flying folks. The Flight Attendants get a list of passengers and those who had a * by their name were the CO STAR gang of which there we very few.
Now that I'm off my double secret probation and on triple secret I can tell no more.