Legal issues will limit their scope, IMO. It's definitely not in the interest of big business for these to go mainstream, so lobbies will fight to make them illegal due to the concern that joe nobody will print a fully auto bazooka in his back yard. Only time will tell if and when they'll push through to the mainstream, but just something I would consider prior to investing. I can tell you though that, Chinese manufacturing companies will be using them if it can make them more productive/efficient.