Growing up outside the US, I always had ID; in the US I don't HAVE to carry it but I always do, what if I'm hit and run like that army guy whose kids were then left alone for 4 days with the elder (3) dealing with the younger (10 months) till the wife, also in the military, called to wonder? Basically I have fear of ending up J. Doe somewhere, I'd rather be identified. Look at Singapore, isn't it, that has the one-card-for-all? All you lose is your privacy, which is overrated anyway...