There is an easy way for Marriott to block theese accounts
There is no way new account starting with 50 nights or 40 nights and 10nights meeting.
Marriott should check for new accounts with platinum for 1-2 month period and block them !!
or Marriott should sell platinum for less like IHG Ambassador (hate the idea) but it's a way to stop this game

by the way they pay more than what they got in my opinion its not worth more than $500