I'm not sure if Google is "corrupt" or not, but I've been reading Thiel's new book and he makes a strong and simple case for Google being a monopoly (and this maybe being OK).
If you are wondering why they are a problem, you might read "The Jungle", or any history of the era of the big industrial trusts. Or you could read "When Wizards Stay Up Late", a history of the Internet's invention. AT&T, the communications monopoly at the time, was a big barrier to the development and growth of the Internet. And, from their perspective, rightly so: they made a zillion dollars from charging for voice calls, something everybody now expects to be free.
In any case, AT&T was a legal monopoly, not a market player with less than 70% of market share like Google (according to comScore). The lessons are not necessarily directly applicable.