Agree, and I have never been asked by an FA to show credentials, but now that I am forewarned, I will pack my state license card in my travel wallet for my trip to Europe in May. Actually, I just renewed my license last month, maybe I'll take the expired one (expired 02/2011) and not risk losing the current card. The card DOES say (in California) that one is to carry it at all times, but I don't know anyone who does. I make multiple photocopies of mine and use those for insurance companies or hospitals who need a current copy on file.

I carry my original card in my car's glove box in what I call my "club card wallet": a spare wallet with club cards for PetSmart, Staples, OfficeDepot, etc...places where I shop occasionally, but not as frequently as the markets where one can key in a phone number to access club discounts without having to scan a physical club card. My AAA card is also in that wallet. That way, I can use a slim wallet with only six slots for driver's license and frequently used credit cards. So my license card is "usually" with me if I drive somewhere, but normally on a trip by air or rail I leave it behind in the car.