Why nobody's built a startup around this already:
(a) There's no money to be had. A company that offered to solve your distributed problems using distributed JavaScript could only charge as much as the spot price of buying EC2 instances. Otherwise, you'd just buy the EC2 instances and solve it there. A problem not amenable to solving with temporary machines wouldn't be amenable to solving with times slices of JavaScript running on webpages.
It would take millions of page views to get the CPU-time equivalent of an hour running compiled code on an EC2 instance. That means the eCPMs the company could reasonably charge, or pay its publishers hosting the code, are thousands of times less than they earn from advertising.
(b) It's a net negative for the economy. Distributing work through JavaScript on webpages is an involuntary donation from employers/schools moreso than the person behind the computer. That extra expense with no gain for the business/school has to be made up somewhere -- higher prices or lower wages/employment.
(c) It's a net negative for the environment. The problems could be solved faster on bare metal with server-class hardware, concentrated in data centers built where energy is the cheapest, usually because there's solar/hydro/wind generated nearby. Solving them on desktop/mobile CPUs, in an interpreted language, powered by coal-generated electricity, would be a waste you'd measure in tons of CO2 that didn't need to be released.
(a) There's no money to be had. A company that offered to solve your distributed problems using distributed JavaScript could only charge as much as the spot price of buying EC2 instances. Otherwise, you'd just buy the EC2 instances and solve it there. A problem not amenable to solving with temporary machines wouldn't be amenable to solving with times slices of JavaScript running on webpages.
It would take millions of page views to get the CPU-time equivalent of an hour running compiled code on an EC2 instance. That means the eCPMs the company could reasonably charge, or pay its publishers hosting the code, are thousands of times less than they earn from advertising.
(b) It's a net negative for the economy. Distributing work through JavaScript on webpages is an involuntary donation from employers/schools moreso than the person behind the computer. That extra expense with no gain for the business/school has to be made up somewhere -- higher prices or lower wages/employment.
(c) It's a net negative for the environment. The problems could be solved faster on bare metal with server-class hardware, concentrated in data centers built where energy is the cheapest, usually because there's solar/hydro/wind generated nearby. Solving them on desktop/mobile CPUs, in an interpreted language, powered by coal-generated electricity, would be a waste you'd measure in tons of CO2 that didn't need to be released.