As long as you stay ahead of competition or make simply better products it will work. Someone might steal your design, but they still have to manufacture it and parts like pcb, case and so on. This will take certain amount of time and in this time you should come up with new better model that offers more to customers.
That's fine if there's a level playing field. If a manufacturer can steal your design in China and get away with it and you can't do the same in the US then you're stuffed. And that's what's happened.
