I believe most 747-400 airlines have this in the their MEL/DDG's (or, rather, their CDL's.. Configuration Deviation Lists).
"Remarks and Exceptions:
1. One may be missing
2. With missing Winglet, reduce the performance and structurally limited weights by:
Takeoff and Landing - 9435Kg
Enroute Climb - 4536Kg"
A marketing ploy further disguised with a weight penalty? Cynic I am, but not that cynical.
Regards.
Q.