I never understood the lamentation of Europe not having an internet giant and I mean it as a question. Does it matter whether the companies are American ? I mean their economic contribution are taxes and jobs. Companies would pay as little taxes as is possible no matter where they are and regarding jobs if these companies find sufficient talent in Europe they would setup offices here (like Google is doing in Berlin). Regarding why there arent internet giants here, who knows and who cares. In this day and age there arent many internet companies being creafed anyway. Would appreciate a counter point.
In terms of taxes a lot of these tech giants (facebook, apple) technically European already, with Ireland used as a tax haven.
They also throw their weight around to get local tax concessions when they do open offices internationally, so I'm not sure it's that great a loss in any case.
I could also see it hurting the greater industrial base, a lot of companies need software but can't afford to compete with silicon valley style salaries.
I think Google has bigger presence in Munich - at least, they are hiring engineers there, not in Berlin. But, of course, this proves your point even better :)