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The biggest threat to Google isn't Apple, Microsoft or Amazon -- it's the U.S. government. Within the next several months, the U.S. Federal Trade Commission may sue Google for antitrust violations. If it does, Google will most likely end up like Microsoft after the government filed suit against it in the 1990s -- distracted and unable to plan for the future. The biggest potential antitrust issue is whether Google unfairly manipulates its search results to point at its own services rather than competitors'. So, for example, the suit might charge that Google manipulates search results to direct consumers to Google Places rather than Yelp or to Google Shopping rather than Pricegrabber or Shopzilla. Another potential issue is whether Google's AdWords marketplace discriminates against ads...