Google's core technology is search facility. If someone does this better than them, then there will be no monopoly. The core feature of printing press stood as is for longest period of time (even Xerox did not bring anything "new" to the table). That's, until the Internet in fact, was able to put a dent on the core invention of printing press. People are now reading on their screens, where as previously, they used to read only on the paper.
You are stuck with the short-term view of monopolies and privacy issues. We wouldn't be surprised if there was a big brouhaha over privacy during the time of the invention of printing press (ask any religious scholar what they have to say about the history of churches against the advancement of technology and knowledge).
The problem is, this isn't necessarily true. Microsoft used to make the same argument in the '90s. The point is when you get entrenched in so many areas it becomes hard to switch. It's a network effect of information rather than people. There would have to be a significant improvement in order for people to switch (with some other motivation, like political).