It has been said (though not in that article) that the Pacific Ocean is the scar of the whack. So if the whack hadn’t happened, would Earth’s crust be all continental? In that case the plates would likely be much less mobile, and most of the big mountains would be volcanic, as on Mars.
Although a big whack may be necessary for plate tectonics as we know it, it’s apparently not sufficient; Mars is also thought to have had one, forming the northern lowlands.
Err, I might be wrong, but I think that the Fission theory posits the Pacific Ocean as the effect of a moon creating event:
http://en.wikipedia.org/wiki/Moon#Formation
(normal caveats apply)
Thanks for the confirmation.