I bought 3 of these kind of adapters.
They have a power plug on the receivers. Then you can use them as you would with a normal usb connector.
1 is used with a usb hub for a wireless keyboard and mouse + external dvd burner + occasional external storage ;
1 is used for motu midi express 128 (4 midi keyboards and 3 fader controllers) ;
1 is used for a wireless keyboard and mouse (second Daw).
But if your passive usb extension works, hey, keep it.
Have you tried to test the Webcam plugged straight on the comp to troubleshoot ?