I agree that write once run anywhere is never quite so simple, but > The reality is, you are going to either target NaCl on Chrome, asm.js on Firefox is an ov

I agree that write once run anywhere is never quite so simple, but > The reality is, you are going to either target NaCl on Chrome, asm.js on Firefox is an oversimplification as well. Many asm.js codebases already run well on Chrome, and that will continue to improve, for the same reasons that all browsers are now fast at SunSpider, Octane, Kraken, etc. But again, sure, if you need full performance everywhere, you may need to target multiple platforms and not just one. Some games might need to do that, but not all.