It is advised to brush your teeth at least twice a day, but when? Just before bed is a gimme because you're about to lie mostly still for 6+ hours. Best to not leave food particles to fester.
What's the best time for an earlier brushing? After breakfast? After lunch? After work/school?
Plus, what's up with TV and movies having breakfast scenes where they get up and head right out the door? Did they already brush and now they're going to leave food to fester all day? Eww.
I think the problem with brushing too many times is that the toothpaste itself is also somewhat abresive. So, brushing too often will result in you destroying your teeth. Especially if using "whitening" pastes.