I think I'm going to go ahead and order one right now (if I can find one in stock). Just an investment, I personally think they are useless toys when it comes to people who don't have nefarious uses.
But realistically, a 'bump stock' type device can be made with a rubber band and a belt loop. If someone wants to get around this, it takes a few minutes to do it at home.
Video, just a rubber band to do the same thing: