Global sources are fine, as long as you understand what they are. Global sources stay loaded even when they are not on the scene you have selected. Usually, this isn't necessary, because unloading them on scene switch gives better performance. However, some sources like Webcams and capture devices work better as global sources because you aren't turning the device on and off all the time when you switch scenes. Also, some games work better when captured with game capture as a global source, so that you aren't constantly hooking DirectX.