Originally Posted by chucklesR
Right - instead of leaving a MMSI radio when you sell a boat, you MUST take it with you, or put up with the risk that the new owner will abuse it.
Apparently you can cancel your MMSI registration. From the MMSI FAQ:
"Go to BoatUS - Maritime Mobile Service Identity - MMSI Registration
and click the Login option. Login using the login and password that you chose when you registered or that was assigned to you. (If you do not remember your login, choose the option to have it e-mailed to you). Once logged in, choose Cancel MMSI Account from the menu screen."