This book is proof that economists don't inhabit the same planet as the rest of us. Economists start from the premise that humans are rational beings, weighing up costs and benefits before making a decision about "resources". The rest of us know that human beings are irrational creatures, driven by prejudices, fears, ideologies, group pressures, and so on.
Whilst the subjects discussed in the book could be thought-provoking, the thought is more often along the lines of "that's a bit of a leap of logic" or "you've omitted an equally valid conclusion".
The example that leads to the title is a prime example of the failure to think a little more carefully. In essence, the idea is that if an uninfected guy goes out and picks up an uninfected woman, she will be saved from a one night stand with an infected partner and thus the spread of AIDS is reduced; whereas if he stays home, she will end up with the infected guy and spread the disease. There is no mention of the odds she'll become infected, no mention of what happens when the virtuous cycle is broken (a massive *increase* in infection rates); just a rather simplistic approach to the problem.
Another example: he postulates two groups, one a religious group that adamantly opposes porn, and the second a porn-loving group that wants to abolish religion. His view is that by abolishing both porn and religion, everybody becomes happier because the object of their ire has been removed. Unfortunately, the opposite (never mentioned) is the more likely outcome: everybody is now unhappy. Why? Because people put more weight on issues that affect them personally than on those that affect others. Therefore, by removing something they love, you have taken away something personal, which will outweigh any happiness gained from knowing that at least their opponents are now deprived of their particular "object of desire", for want of a better term.
Finally, if you're a liberal, you may find some parts cause you to become rather agitated...