This seems like more of a ChromeOS move to me, so that you can run native code on Atom and X86 machines. The knock on ChromeOS is always that it's "just a browser". I seriously doubt anyone is going to write their Etsy storefront in NaCl. The benefit here, of course, is that if someone does write the next Photoshop for ChromeOS machines, it should also run fine in OS X, Windows and Linux. Seems like a win for portability to me.