One of the major reasons PNaCL is "non-viable" are the comments like this one, calling it non-viable, and insisting on a JS-everywhere future.
If Mozilla et al spent half as much time trying to work with Google as they spend badmouthing everything that isn't JS, we'd have some solutions by now. These are political problems, not technical ones.
Yes, I think that demonstrates my point, given that the author is Brendan Eich, CTO of Mozilla.
Mozilla has had years to contribute something meaningful to the conversation, and instead they've consistently badmouthed Google's efforts while watching the meteoric rise of native mobile development.
So now they've finally brought asm.js to the table; a Mozilla-flavored common bytecode, which is what we've been wanting for years, and exactly what Eich and Mozilla said was wrong for the web: http://en.wikipedia.org/wiki/Google_Native_Client#Reception
Fine -- if using javascript to encode a bytecode is what it takes for Mozilla to actually take the need for a common bytecode seriously (and admit that DOM/JS/HTML/CSS is perhaps not adequate), then I won't look a gift horse in the mouth. I just wish they'd figured out the need for post-JS webapps a little sooner.
If Mozilla et al spent half as much time trying to work with Google as they spend badmouthing everything that isn't JS, we'd have some solutions by now. These are political problems, not technical ones.