Someone flung from a car won't damage you, but have a look at videos with crash test dummies, where a passenger in the back isn't wearing a seat belt. Them being flung in to the back of the driver's seat creates a huge impact.
The windshield won't be flung anywhere, but an electronic device will. Getting smashed in the face with an iPhone going 50Km/h is going to do some damage, rounded corners or not.
