Kanex's DualRole is a USB 3.0 hub and Ethernet adapter for modern MacBooks
 

The glitzy sheen of that Retina Display MacBook Pro or MacBook Air probably tarnished a little when you realized you'd need to sacrifice a USB or Thunderbolt if you wanted Ethernet connectivity. Just in time for Macworld, Kanex is shuttling out DualRole, a three-port USB 3.0 hub and Ethernet adapter that'll swell your connectivity options while on the road. Bus-powered, you can also add a 5v power adapter to juice your gadgets at the same time. It'll set you back $69 and is available from right about now.

http://www.engadget.com/2013/01/30/kanex-dualrole/