Now, as is so often the case with these kinds of contentious theses, there's no doubt a weak version, which is more or less unexceptionable but banal, and a strong version, which is interesting but more or less dubious. The weak version in this case would simply say that these sorts of "nudges" are what designers of systems and objects deal with all the time -- they're directly related to the designed purpose and function of the system or object itself, and as such have always been a big part of what constitutes good design. The strong version, however, relates to much larger and more ambitious objectives for "improving" people's decisions in areas that may be far removed from the particular object or system used to provide the nudge. In this version, it seems clear, we're talking much more about manipulation of decisions than we are about good design.
Kenneth Anderson's post on "Leviathan" at Volokh is again pertinent to this version of a kind of sneaky authoritarianism:
... the liberal authoritarianism that started to take hold in the first days of the Clinton administration, but then went into retreat, and has now reasserted itself with nudginess — the return of the repressed — is not Hobbesian in another, utterly fundamental way. Today’s progressive authoritarianism is not about an institutional settlement to the war of all against all, every man for himself and God against all, but instead an assertion of therapeutic authoritarianism. It will not just provide you with security against your neighbor — it is for your own interior, psychological well being, to help you be simultaneously a better person and a therapeutically more happy one. Contemporary liberal authoritarian impulses unite the prosecutor and the therapist, so as to produce a prosecutor who is as much a member of the “helping professions” as the psychologist (or, more exactly, the behavioral economist nudging us along), on the one hand, and a therapist who is armed as much as the prosecutor with the powers to compel, on the other. It is not Hobbesian, but something frankly far more ambitious.So ambitious, in fact, that it feels the need to disguise itself. But the disguise doesn't let it escape from the problems inherent in any form of authoritarianism, the first being the simple one that in a society of free adults no one or no group of self-styled elites has the moral/political right to tell the rest what's good for them, whether that "telling" is done via overt command-and-control modes, or more indirect taxation and price manipulation means, or via the behavioral economic "nudge". The second problem, related to the first but independent of it, is the Hayekian "knowledge problem" -- aside from moral right, no one has the information needed to make life decisions for others, and this lack includes any group of "scientific" technocrats who are embedded in their own lives, and their own values, beliefs, and biases. Merely tacking "libertarian" onto "paternalism" won't get around these old and familiar faults.