An abadá is a shirt which works as a ticket to a party. It’s like an ultra-violet stamp or a bracelet. For the many “blocos” (or bands) that play on the streets during the carnaval festivities in Brazil, it allows some form of control of who can get in, even if the space where the party is going on has no walls or fixed limits, as the “blocos” parade on the streets, sometimes through long routes.
That would also allow the bands to parade with larger and larger amounts of people attending. That is, it is an attempt at avoiding taking the carnaval indoors. And this is very important from the perspective of carnaval traditions, for the parading of the bands is in many ways what creates the exhilarating openness and freedom of the carnaval.
Nevertheless, the use of abadás creates some strict limits between belonging and not-belonging, between being IN and being OUT. This rapidly creates inflation of the prices of the abadás and indirectly of the whole carnaval experience. And this, in turn, makes carnaval only available to the elites (and tourists). Or more precisely, it splits carnaval in two, one rich and the other poor. Which, by the way, is exactly what was not supposed to happen.
What that means is that the abadá is neither a good thing nor a bad one, but a thing that has a strong impact on the carnaval. There are places (like Recife) where the idea faces strong opposition, in ideological basis. There are others where it is taken for granted.
Obviously, once the abadá is introduced to the festivities, it won’t go away. Because, in many ways, it works inside this whole carnaval system. It has a strong appeal, it is felt to be a strong solution to perceived problems, when considered from the individual perspective, even if in a greater scale it generates many other problems. I could say that the abadá is a emergent property of the carnaval system — once it happens, it tends to propagate itself.
If one takes emergent properties as natural, meaning either that it is the way things should be, or that there is nothing that can be done to avoid them, then carnaval should embrace the abadá as the only means of access control. But that would change many of the best characteristics of carnaval. The fact that a property in a system is emergent (self-perpetuating) cannot be basis for moral judgments on the system, like for example to judge if the abadá is a good thing or a bad one, and furthermore if it should be used or not.
Nevertheless, this idea (that self-emergence is justification enough) lies dangerously at the very bottom of the current scientificist world-view. The best example is the natural selection. In a way, “the survival of the fittest” is used to say that this “fittest” is good, and in this way it generates a moral of nature. That says that the way of nature is the only way even if it isn’t. This same moral is the one that says that nature must be preserved at all costs (and, therefore, blinds the world to the possibilities of negotiation in the ecological arena).
Whenever this happens, in effect we are stopping all conversation and trying to force one world view through force. Which sometimes is needed, but also is a sure way of diminishing complexity. And there is a thing called the law of required complexity that states that to survive in an open environment a system needs to be at least as complex as the threats it is facing.