One of the key features of the web is that it’s pretty safe to click on almost any link. Your browser can fetch code from some unknown server on the internet and run it.
As it stands today, Native Client is a software “sandbox” meant to securely run native code inside a browser. Native Client can give you a tremendous improvement in performance compared to other options for running code in the browser. The rub is that Native Client isn’t the web – at least not yet. It will soon be an integral part of Google’s browser and its browser-based operating system.
Chrome will only accept Native Client applications distributed through the Chrome Web Store, and Google will only allow Native Client apps into the store if they’re available for both 32-bit x86 and 64-bit x86 (the ARM version of Native Client is not yet ready for prime time).
The problem for wide adoption is that Native Client hasn’t been integrated with other browsers. It hasn’t been standardized. Is this development direction good or bad for the web I am not sure.