I am running 6 U1's  on a Anker 9 port USB 3.0 hub.    No issues what so ever with power.  I would test to see if I could run more on it,  but only have 6 U1's.

This is the hub  http://www.amazon.com/Charging-Adapter-VL812-B2-Chipset-Firmware/dp/B005NGQWL2/ref=sr_1_1?s=electronics&ie=UTF8&qid=1389657073&sr=1-1&keywords=anker+9+port