Is google a monopoly?

Through the last ten years google has been growing fast, gaining many loyal users and creating a huge business opportunities around it as advertising and search engine optimization. Other companies have tried to imitate the google way of work and started to create its own text advertising programs, even started to compete Google adsense in the web advertising market.

Moreover, google's page rank has become a very trusted criterion in websites evaluation. Highest PR owners sells more expensive ad spots and even in website markets as SitePoint (where people buy and sell websites) people refer to PR to fix their first price.

And here we come to the point where google used his weapons to kick his competitors by cutting down PR from their affiliates. So is that an antitrust move? PR is google's tool and he can make what he wants with it...

Google has also slammed paid links users and cut off their PR. As we all know google is responsible of the relevance of his search results and he don't want to have links to show up first because its owner paid more ! But don't you think that Google exaggerated by cutting down PR that way? I think that wasn't because of the relevance of the search engine but to make bloggers and webmasters get away for paid links programs as payperpost. Because these programs were loved by bloggers because they generate a respectable revenue and for advertisers because it creates better keyword density to their link.

Finally, I am afraid that Google gets to the point to be a beast that can not be fed and turn into a manipulator of the whole network because it started to show some signs of Power and monopoly... What do you think?