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Bloggers have speculated that Google and other folks working on Android phones have been hesitant to implement the pinch-to-zoom multitouch feature in their devices because Apple supposedly holds a patent on it. Nobody's sure whether or not the patent would actually hold up, or whether Apple would dare take anyone to task for using it. Other phones — including the Palm Pre — have gone ahead and taken the risk, and they haven't experienced cripplingly adverse legal consequences yet.
It's possible that Apple itself is not sure that it could win the battle, or that there's a "mutually assured destruction" aspect to the situation; Apple has likely traversed into some gray areas as far as patents go, too.