I have a Geeksphone Peak running FirefoxOS 2.1. The Network Sharing using USB does not work. Originally, the device shipped with FXOS 1.5 and that did not work either. I found this article: https://support.mozilla.org/en-US/kb/share-your-internet-connection#w_share-your-connection-over-usb but it does not show any specifics. I connected the phone to my Macbook, and now what? BTW I have the same problem on Windows 7. I feel there should be some extra information. Network sharing using a Wi-Fi hotspot also does not work, the hotspot is not visible on any of my laptops or tablets.