Privacy concerns aside, this is a "half a loaf of bread is equivalent to no bread at all" argument. Yes, catching progressively more sophisticated signals gets progressively harder. That doesn't mean basic mining is useless. It reminds me of the argument that banning soda sales in schools is useless because kids could just go to a store across the street. They could, and some will, but taking care of the path of least resistance can go a surprisingly long way.