Most of the time I ride with no identification whatsoever (too much extra weight).
No ID?
In a serious accident where you are unconscious, that could prove to be a real (and very unecessary) problem for the emergency crews, and notification to someone who can speak for your rights and actions in a hospital. I would think that a copy of your driver's license or at least a card about who you are and who to notify would not weigh very much. Perhaps .1 ounce??