From a Newsweek article:
What began as a trickle now has turned into a tidal wave. In August Google announced it was activating 200,000 Android phones each day. On at least one day since then, that number surged to more than 250,000, Rubin says. Android now has leapt past Apple to become the biggest smart-phone platform in the United States, the third-biggest worldwide, and by far the fastest growing.
Microsoft last week sued Motorola, alleging its Android phones violate Microsoft patents. Similarly, Apple has sued HTC over its Android phones, and Oracle has sued Google, alleging Android itself violates Oracle patents. If nothing else, the lawsuits demonstrate that rivals recognize Android has become a serious threat.