usbview error on startup

You need to run the program as root.

In a text terminal/shell, use:

sudo usbview

(You need to enter your password)

If you need a GUI command, use:

gksu usbview

The full error message in that error dialog window is:

Can not open the file /sys/kernel/debug/usb/devices

 Verify that you have USB compiled into your kernel, 
 have the USB core modules loaded, and have the 
 usbdevfs filesystem mounted.

It lists various possible cases of the problem - except the most common one - that is confusing.
It made me also think that it's probably not the problem, because I would expect it in the list. Actually, one could see the message as a minor bug.