Anyway I think that a Webcam cover should be a default on webcams, not only for privacy, but also for th same reason why Cams and binoculars have caps by default, to protect the lens. If you use a tape, to avoid glue on the lens, you can cover the intern part which is over the lens with a piece of paper

For this the best AV (100% proof)

(A piece of tape also works fine)