As I'm not a native english speaker and don't expect you to understand the title, I'll just show an example:
Add
trace (NAME + ": ", viewComponent);
in a mediator constructor.
Instantiate ShellMediator once and then WindowMediator twice:
ShellMediator: [object Shell]
ShellMediator: null
WindowMediator: [object Window]
WindowMediator: null
WindowMediator: [object Window]
So it's like when You execute a mediator's constructor first time for the specific class, You get the constructor executed once more without viewComponent argument...
I'm using Fabrication for Flash, everything up-to-date.
I don't know if this is a bug, it just got me alarmed.