The frat boys in the movie are trying to do that:
Two of Cohen's targets — fraternity boys who made drunken, insulting comments about women and minorities — are suing 20th Century Fox and three production companies. The lawsuit claims that a production crew took the students to a bar to "loosen up" before participating in what they were told would be a documentary to be shown outside of the United States, and that they signed waivers after drinking heavily. Studio spokesman Gregg Brilliant said the lawsuit "has no merit."
All sorts of interesting questions crop up on the basis of that quote about when a waiver is clearly understood, about whether what Cohen did with his unwilling co-actors was ethical and, most interestingly, whether you can sue someone because you have shown yourself to be a racist and sexist quite voluntarily, but only because you thought it would be some other people who will learn it, not your own homeboys.
I haven't seen the movie yet, and I'm still deciding on whether to see it or not. But I've viewed several YouTube cuts of Borat's humor, and I can guess what the movie will be like.
Cohen's M.O. is to take a joke to its very extreme, where it almost stops from being funny or indeed does stop, and the laughter is at least partly a response to the shock that he actually did go that far. An almost painful kind of laughter.
I don't mind that kind of humor too much, because it can even teach me something about my own ugly aspects. What I haven't liked in the short bits I've seen is the cruelty of some of Cohen's humor, the way it laughs at others, not at Cohen, and from a higher moral perch. Perhaps because the basic idea in the movie: to film people pretty unaware of the plot, is in itself a cruel idea.
Borat is still very funny, though.