But in the book "How We Test Software at Microsoft", they mentions Microsoft test USB implementation with "USB Cart of Death", which including 10 of 8 port usb hub:

https://books.google.com.tw/books?id=X5lCAwAAQBAJ&pg=PT414&l...

Edit: Maybe it is no issue with USB hub, but not work with too many usb controller (USB port to MB directly)?