I recently bought USB off/on switches [1] for the external webcam and microphone on my desktop. I think they control the power line and not the data lines, but they do the trick. Reduces port fatigue and USB orientation frustration.
turns out it was leeching power from another still-active device through its data pins!
there was not enough power flowing through this way to actually do something, but there was enough to keep the brownout detector from kicking in and resetting the chip
Some 10-15 years ago someone built dirt simple radio tags this way. Just a microcontroller, with a capacitor and an antenna trace connected to some io pin. I loved that hack.
In related news, I used an old Android phone and DroidCam over USB as a webcam. The picture quality is stellar, much better than any webcam you might find, and it's very simple to stop it by unloading the driver (I know, I know...).
It's really, really helpful to figure out which wall wart goes with which device.
Another tip I learned from another. You know those green plastic tabs that keep a bread bag closed? They clip onto a cable nicely, and write on them with a sharpie which device the other end is attached to. That really helps with the rat's nest of wires under my desk. One of them says "cam" on it :-)
Also, with respect to cables, this is really why we need tri-colored braided cables from a reputable dealer (ANKER!?): white, black, gray, blue — that gives 64 possible combinations!
I'd consider that an honor.