It seems like a lot of people, and most of the story for that matter, have focused on the tennability of arresting people for crimes that they have yet to commit, but I think that there might be another, more important issue. Since, unlike in the movie, it seems that the precogs can detect any or almost any crime, then it is virtually impossible to commit crimes in this society. And, if the state can define whatever a crime is, than it seems that precognition presents the ultimate tool for the creation of a total state- one where any commision of a proscribed act could be stopped before it happened- resistance would be stopped before it occured. Really, it seems like, due to that potential, precognition is to much power for anyone to have.

I think that this ties in to a part of the main plot- whether people in their society have free will. Even if the state justly defines crimes (for example, making the proscription of the excersize of fundamental freedoms and irrevocable crime, regardless of anything like a constitutional amendment that could change other legal provisions, thus stopping totalitarianism before it starts), I think that it is important that people have the free will to commit crimes, even if they will suffer the consiquences. One of the most important elements of humanity is the ability to control your own destiny- sort of like with BNW, I don't think that you can prohibit self-destructive actions, even on the level of an entire societies.

P.S.- sorry about the time. I just noticed that I had only saved this post as a draft- I thought that I had published it, but I just saw that it wasn't up on the page. Good thing I noticed!