Re: Two seperate races being run here
Nokia bought marketshare in 2010 by offering carriers deeper and deeper discounts to stick with Symbian devices, as Symbian^3 got later and later, and then finally arrived half-finished. It was only the release of Symbian/Nokia Belle, in Summer 2011, that gave the platform a genuinely competitive user experience, but by then the damage had been done, and Nokia had already cut it loose (rightly, I think, although I'm not happy about it).
A better example of a pyhrric marketshare victory would be YouTube. It dwarfs its competitors in video [source: http://www.comscore.com/Press_Events/Press_Releases/2011/12/More_than_200_Billion_Online_Videos_Viewed_Globally_in_October ] but it makes not a red cent (net) for its parent company.
I think Apple's biggest risk isn't from Google, but rather from the sustainability of the market they've created. Right now, they are the linchpin in the current mobile-apps bubble economy: millions of dollars of VCs' money is flowing through startups, to app developers, and Apple - those startups launch on iOS first, use Apple hardware and software for development, and make Apple's iOS platform more attractive for end-users - people don't buy iPhones because they're the best experience (they're not, anymore), but because EVERY third-party app worth having is on iPhone. The problem is that these apps are cloud-based, requiring an online service, and a vanishingly small number of these services are viable. Sooner or later, the VCs will wake up to this. If (and when) this bubble bursts, Apple's $80+ billion cash reserve means they'll be fine, but they certainly won't have that $500 billion market-cap anymore.
Google run just as great a risk of being disrupted as Apple do, as they are still heavily reliant on a single commodity service. They have what they believe to be a monopoly on online advertising, and it's bankrolling everything else they do, from Android to GMail to YouTube. If another company were to take this revenue away from them (Facebook, maybe?), then they're in trouble, but again, like Apple, they've built up a nice pile of cash to cushion that fall.
Hardly do-or-die stuff, but there you go...