Pointed toward his 18-acre compound in Marin County, California, Sean Parker rips through the night fog on the Golden Gate Bridge in a stealthy Audi S6 that masks a Lamborghini engine, one pale hand on the wheel, the other toggling through thousands of songs uploaded on the car's sound system.

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But even the iPad, praised for its ease of use, is unsafe to operate with one hand on a steering wheel and a foot on the gas.

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