Anyone who stumbles into your SHAllenge ought to know that JS isn't going to be really competitive, so I think you're good. A warning might encourage them to delve a little deeper. I like that it makes it very accessible.

I assume anyone with knowledge about GPU hashing and the will would be able to steal the top spot very quickly. Assuming seletskiy isn't already that guy. I don't have a good grasp on the compute difference between 8-9 0s and 10 0s in a reasonable amount of time.