It is marked insecure, there is no way mainstream users will mine or even visit a site with a warning like that popping up ...cool concept though

Last time I looked into javascript based mining perhaps a year ago, the effective earnings for a site with a few thousand uniques per day was only a few cents. Considering that a CPU intensive background process will impact negatively upon some of your visitors, is it really worth it?

Happy to be corrected if circumstances have changed since.

Very cool. But also basically malware.

It's not really malware. You're trading some CPU time for content. You do the same thing with your brain when you visit a website that contains ads.

I wonder if it's possible to accelerate this using WebGL?

Google marked it an unsecure website