[MatthewPhillips]

I think it is necessary for the same reason it was necessary for Google to create Chrome to get the other browser vendors to get serious about Javascript performance. Today Javascript is no longer a blocker.

If Mozilla can force other mobile OS vendors to get serious about exposing lower level APIs to the web through (open standard) javascript, it will mean a major win for all smartphone users.

[BrendanEich]

Chronology: Chrome came out in early September 2008. Mozilla's TraceMonkey was under development from April of that year. True, we started on a JIT customized for JavaScript (i.e., not Tamarin) later than we should have, but we did not start because Chrome with V8 was known publicly and already in the market.

I believe Apple's SquirrelFishExtreme work was also going on in the summer of 2008, on a webkit.org svn branch.

Your general point is good: healthy competition helps the web evolve. We got the world we wanted in launching Firefox in 2004. The battle's far from over, what with all the lock-in on mobile devices and in social network sites.