Not related to startups, but: the free market's distorted. Google, Apple, Facebook & co. are quite competitive today.
But they are also sitting on war-chests worth multiples of their yearly incomes (or at least a big chunk of 1 yearly income) and they are close to monopolies in some of their markets.
Even if they'd break down this badly, they'd be around for decades. Heck, IBM is still around :)