Quoting GFireflyE, reply 1
Notice that the first thing he mentions is not enough warning when a city is idle.
And I scoffed and laughed. How could you possibly miss the blinking and fairly large ZZz on the screen? .
I miss it all the time. As I already wrote in one of my comments, the interface is poorly designed and non-ergonomic, because various related pieces of information are scattered to distant parts of the screen. This "warning" is a perfect example because it appears in a section that does not normally contain useful/urgent information.
Take Paradox GUI for as an example - it has a dedicated sections just for warnings, grouped by severity. It also let's you to customize the GUI, so that it can offer popup warnings for events you consider important.