I remember that LiteCoin briefly had this idea, to be easy on consumer hardware but hard on GPUs. The ASICs didn't take long to obliterate the idea though.

Maybe there's going to be some form of pay per browse system? even if it's some negligible cost on the order of 1$ per month (and packaged with other costs), I think economies of scale would allow servers to perform a lifetime of S24 captchas in a couple of seconds.