As a developer writing web applications, I have not found the use-case for WebAssembly, as excited as it makes me about web performance. I think that having it integrated into front-end frameworks could be one such use case (like Microsoft's Blazor).

So if browser benchmarking quality stays the same, in a year browser performance will be judged 20% by WebAssembly bitcoin mining performance and the engines will be optimized for it.

What percentage of sites that use Javascript use it maliciously?

Funny how crypto is often associated with crime.

But at least they are sandboxed! /s