Barbara Ehrenreich is a journalist, who underwent the "experiment" described by the first answer. While the book certainly was insightful, entertaining, even shocking in its portrayal of the working poor in America - many people didn't like it.
The author has been described as a "left-wing liberal," perhaps before but certainly after writing this book. This in itself isn't a bad thing. However, the fact that she is writing a non-fiction book - this certainly raises red flags for those who are not on her side. Many believe she wrote with too much bias toward the plight of those in poverty and against those who aren't doing enough to help. But like the first post says, even through her "experiment" she herself did not fully take on the difficulties of most Americans making minimum or just above minimum wage. (In addition to the car and the extra back-up cash, other complaints include that she also was doing this alone - without children/family to feed, she refused to pool resources with roommates, and she had health insurance had a serious emergency occurred, not to mention, she could stop anytime it got too difficult.)
Because of this - her overall attitude throughout the book (to me and others) seemed a little disingenuous. It was as if she was fighting to be seen and heard because she experienced the life of poverty. But she didn't. In her attempt to paint a realistic, straight-forward, and empathetic tone in her study - many think she failed, arguing that she came across as pretentious and a little snobby - but with a mask of humanitarianism and concern.