[tumult]

It wastes space and then you have to think about a way to display two separate items which represent the same data but which can be in different states.

If you're using the menu bar so much that having it on the other screen causes you to be unable to use the second display, you should consider learning keyboard shortcuts for the menu items instead of clicking on them manually each time. They should be labeled in an application's menus, if it follows Mac design guidelines (and common sense.)

[MaysonL]

And with Snow Leopard, you can assign your own keyboard shortcuts - and they'll even show up in the menus! System Preferencea->Keyboard=>Keyboard Shortcuts->Application Shortcuts (click on the plus sign)