Comment 9 for bug 35004

Further details:

/proc/bus/usb is a pseudo-filesystem that contains special files that magically map to individual usb devices

It's been deprecated and unsupported for a while now, and is on gregkh's hit list of things to be removed from the kernel entirely.

It's been replaced by /dev/bus/usb, a udev-maintained directory in the same format (but using character devices instead of files).

Applications can use this without knowing the difference, with just a path change.

Note that there's no /dev/bus/usb/devices (equivalent to the old /proc/bus/usb/devices file). An application that wants to know that kind of detail would need to iterate /sys/bus/usb/devices or use HAL).

We disable /proc/bus/usb in development releases to prevent any software from using it, and generally encourage people away from it. We re-enable it in the release candidate, but only for the root user.