The problem comes from the standard "your right to swing your fist around stops when it hits my nose". If your weekly yard sales leads to people parked in front of my house every Saturday, and crowds of people that are not the norm for a residential neighborhood, then your right to make a few bucks in impinging on my right to enjoy the house I bought.
Places zoned residential are just that residential, and playing around in the loopholes to run what is essentially an open air thrift store is bull, IMHO. If it were my neighbor, I just might file a civil suit. You want to open a thrift store, go ahead, but not in your yard.
See, one reason we end up with BS laws is that people act in a BS fashion. Like stupid warning labels that we get becuase people wont apply common sense, and then sue when hurt "Dont drop radio in bathtub".