USB 3.0 utilizes the same 2.4GHz frequency band that is used by WiFi. If the NUC is placed too close to the router and USB 3.0 is busy, I believe that it could cause WiFi connections to be lost or interfered with. This shouldn't happen for USB 2.0 devices that are connected to the NUC.
Similarly, wireless keyboard/mouse dongles often use the same 2.4GHz frequency band. You could thus see some issues with the dongle if USB 3.0 is very active.