A less complicated but similar problem to pop ups is the case where declared components will sometimes have their instantiation deferred by Flex.

For example, imagine you have an accounting application with separate sections. You have complex View Components for Accounts Receivable, Accounts Payable, General Ledger, etc. In the MXML for your main application, you have declared a component called AppSections, which is based on the Flex Halo TabNavigator class. AppSections has declared as its children one of each of these custom accounting section View Components. You want to mediate the AppSections component so that other actors can send it Notifications to change the section displayed progammatically if need be. And you also want to mediate each of its children, which represent complex subsystems and likely warrant their own Mediators.