I carry ID on me all the time. Why? because (a) I drive a car, so I need to, (b) because I occasionally write a check or use a credit card and get asked for ID, and, (c) if stopped even as a pedestrian for some reason (which hasn't happened since 1992), I have some way to identify myself so that I don't have to spend a lot of time detained while they sort things out.
I prefer to streamline my life to avoid the possible pitfalls of conflict ... life is easier that way (not to mention the blood pressure stays low).
I can't find a good reason NOT to carry ID on me. Since I'm not stopped by "the man" with any frequency, it's only inconveniencing ME not to have my ID on me - I'm not thumbing my nose at the all-pervasive state and inconveniencing the gendarme by my not carrying ID on me, so why not carry it?
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Of course, an officer in the field could only verify your name with a DL and even then, if he was to issue you a citation or make an arrest, he doesn't have to accept said verbal memorization as the gospel truth since <gasp> some people do lie about such things. But, if only detained, that should generally be sufficient to avoid an arrest for failure to ID.

