That you cannot have the name BUNGiE as your UniqueID. If you try and use it you get an Error (41), If you try and use a name that is already in use you get an error (200). There is a difference.
What have you learned today about Bungie.net
English
#TIL
-
They didn't let you use some letter/number combinations as your calltag or whatever the hell they were called in Halo, so it makes sense they wouldn't let you use some names as your unique ID on here.