Yes but black tape costs 1/50th the price of these and people even give webcam covers away at events.
I think the black tape is cheaper, though I use part of a post-it.
After using one of these devices for a day, I've gone back to black tape. Why? Because you're never certain the camera's blocked with a 2-position switch unless you look each time, whereas with tape it's ALWAYS where you want it.