Hey, Microsoft and Apple have tons of cash and do nothing interesting with it. The reason behind 'sudden' GM's death isn't shitty cars, they've been shitty for a long time. GM is dying because instead of trying to build a decent car business it essentially transformed itself into a bank (GM Financial) which found nothing better to do with their cash than "invest" them in guess what.
Now look at startups: have you ever seen a TechCrunch announcement that was in any way memorable? I see nothing but a never-ending conversion of MySQL tables into HTML pages, or wrapping OSS projects into HTML/JS UIs hoping to get rich quick: the distance of their "R&D trajectories" are measured in months and working prototypes are expected within weeks from the first napkin drawing.
Now look at Google, a poster child for "SV magic". Google is a creation of two Stanford students, i.e. an academia project turned into business (just like Symbolics and DEC had grown out of MIT). Entrepreneurship or corporate R&D had nothing to do with Google's success what-so-ever.
Businesses don't give a shit about innovation, technology and science. Their goal has always been quick profits, for which there always seems be some kind of a scheme to take a ride on. Look what IBM, HP, AT&T and Xerox, former think tanks, transformed themselves into. IBM especially grosses me out with their "we're a services company" bullshit. So is my pet sitter.
It is corporate never-ending search for increased efficiency that essentially kills innovation because the process of inventing is terribly inefficient by its nature: it's unpredictable, cannot be put on schedule, you can't budget for it and the outcome isn't guaranteed: find me one MBA who'll like any of the above.
I've never been especially smooth with my writing, given that English isn't my first tongue, but Phillip Greenspun has: http://blogs.law.harvard.edu/philg