Most people wouldn't think to do it. But if you have a busted tail light of which you were not aware, for example, rest assured that you'll know about it after passing through a "DUI" checkpoint.
Come on. This is a weak argument. Most people are going to get this app so that they can drink and drive, not to avoid getting busted for a broken taillight.
That may be the case, but my point (which I tried to infer, if unsuccessfully) was that these are much more than "DUI" checkpoints. Apple shouldn't be swallowing the government's line about this.