I think the significance of the errors depends on whether the film is truly attempting authenticity. Indiana Jones doesn't bother me -- those movies were just intended to be dumb fun anyway, kind of like James Bond. But Gettysburg, Matewan, and other films that aim for historical accuracy should be held to a higher standard. And then there are all those historical dramas in which everyone is so damn clean, well-dressed, and healthy (at least until they die romantically, always somehow managing to eke out a poignant last quote before gently expiring).