Windows apps on non-WinTel. Make it a x86 emulation, Google could buy wine and/or ReactOS
Thanks to @BlueGreen for doing the hard work and reading the white paper. I agree that reliance on x86 hardware limits NaCl.
However, if an x86 emulator was built and google ported free WIN32/Windows OS alternatives such as WINE and/or ReactOS into Chrome then one could run standard Windows applications within Chrome independent of hardware.
Which makes ChromeOS on alternatives to x86 such as ARM more appealing as it cirumvents the blocker: "compatibility is the enemy of competition" because access to the vast, comprehensive x86 Windows application base would be available on non-x86 and non-Windows machines. Non-x86 netbooks suddenly become more appealing with the WinTel monopoly challenged.
Sure, an x86 emulation on non-x86 will run slower than on x86 hardware but it might still be usable. Perhaps some clever folk could come up with optimisations such as JIT. Lots of expertise out there regarding emulation: consider Apple's Rosetta for running PowerPC based programs on their Intel machines.
Will Google buy WINE and/or ReactOS? Perhaps at least we can expect more Google Summer-of-Code seasons where these programs are developed.