Depends. If you were saying something like "Hey, what have you got in the privileged-information category?" Then "privileged-information" is a compund adjective modifying "category" and needs a hyphen.
People with backpacks on the subway are supremely annoying. They love to turn from side to side smacking everyone in a 100 degree arc behind them. It should be legal stomp on their toes, I think, but banning backpacks outright is going too far.