There's no requirement to sign a bluey if the reservation is made on-line. For other reservations, the bluey isn't necessary if the pax have the same last name as the person holding the miles. It gets a little more complicated if the pax are family members with different last names. My wife has a different last name than mine, but fortunately we have the same address for our MP accounts so I haven't had to do anything special for award tickets with her as a passenger. Sometimes it takes a little effort speaking with a supervisor to get this to work out, however.