All ideas are welcome. Just because the Idea doesn't make it into the product immediately does not make it a bad idea.
It would be helpful for server maintenance and what not to be able to "push" a message (green box notification) to all users of the system to be able to schedule maintenance and what not.
Also if you could schedule the message for a specific time - so say "we're going to reset the server at 5pm today" and have it disaply to everyone who logs in between now and said time.
You won't be notified about changes to this idea.