Interesting argument regarding the #4 and #9 thing. But I think most of that has to do with the fate that there have been plenty of HOF players that have worn both numbers, wheras who has really worn #66 or #99 with any conviction?
#4 - Bobby Orr, JEan Beliveau, Red Kelly, Scott Stevens.
#9 - Gordie Howe, Maurice Richard, Bobby Hull.