So sometimes you want to charge something from the usb of a macbook while the macbook is closed (sleeping, or whatever this functionality is called nowadays). Other manufacturer like ASUS have one usb port that is always powered, while the rest are not.
This is what I found.
With macbooks that's not the case. If the macbook is closed, all the ports are unpowered.
If you start charging something while the macbook is open, and then close it, it will continue to charge it while closed. Which is a really cool, because initially I thought all the ports are unpowered.
This is a bit annoying, because if closed, you have to open the macbook first.
Tested on the latest MBA.