There may be a case where you have servers with the same exact short name, long name may be slightly different. These servers are often split between Production and Staging (Testing) servers. Before this was not a possible configuration.
Currently as of this writing, you CAN have both servers live in harmony as long as one of of the servers is registered and the other is unregistered. You can not have servers both attempt to use the same name otherwise you'll be fighting for listings