Growl notifies the application that posted a growl message when the user clicks on it. In most other apps when a growl notification is caused by activity in a specific window, the app will bring that window to the front when you click on the notification. For example, in Firefox if there's a growl notification that your downloads finished, the download manager comes up when you click on it, and a notification about addon updates being available brings up the addons manager when you click on it.
So when I get a growl notification that a terminal just rang a bell, for example, clicking on that notification should bring said terminal's window/tab to the front when I click on it.
Nice idea.