If the person who the cars name is registered under reports the car stolen, you could find a sticky situation. Its best to get the car in your own name so you won't have yo worry. As long as you follow speed limits and other driving laws you shouldn't have to be concerned w/ being pulled over
That's highly unlikely that an insurance company would issue a policy in a name that was not on the owner's card. But to answer your question, the insuance card, even if it's in your name, does not give you the authority to use the car. Only the actual registered own can give that permission to you. So if you use it without that person's knowledge or permission, you are technically stealing the car.