On page 28, Ehrenreich discusses her failure to make as much money in tips as she had during the tourist seasons.
On page 35, Ehrenreich reports how her supervisor at a restaurant gave her friendly advice because she was failing to do her job quickly enough.
On page 57, Ehrenreich recounts how, when she once failed to pay her rent on time, she was locked out of her apartment.
I largely agree with #2: Ehrenreich was not truly committed to living in a budget and working hard to make ends meet. I don't have the book in front of me, but it seems in my admittedly faulty recollection that she spent more time complaining about conditions than actually working. Financial writer and radio host Dave Ramsey regularly advises his callers to work two or more jobs to pay off their debt; Ehrenreich was working one job with no debt, but didn't need to make the hard decisions or efforts that people without a fallback position must.
For a counterpoint view, check out these two stories: Charles Platt, novelist and Wired contributer, worked for a time at Wal-Mart and had a vastly different experience, while college graduate Adam Shepard voluntarily stripped himself of his possessions and worked from homelessness to a state of reasonable comfort.
I don't perceive her work as being a failure. I think she accomplished exactly what she hoped to do - she experienced living under minimum wage conditions and provided her perceptions and insights into the experiences she had and that she observed among her coworkers. She recognized from the outset that her experience was going to have significant differences from that of other minimum-wage employees because she did have access to resources that they did not. This doesn't mean she failed in what she attempted to do, however. It means she had a different set of rules to play by, but I think she would not have been as credible if she had not tried to experience the lifestyle for herself.
In order to list ways in which she "fails," you should probably first establish what it was she was seeking to accomplish, which is several different goals, in writing this book.
I think one of her biggest "failures" in getting her message across, came in her initial plan to personally prove how Americans living on minimum wage don't have much of a chance at survival. One of the biggest flaws (as critics so readily point out) in her "experiment" was that she wasn't truly reliant on minimum wage to actually live. She had a fall back, at any time. She could bail out if things got too difficult. She had medical insurance and a car. Such luxuries allowed her to live with less fear of injury and sickness. Such luxuries opened up her geographical range of where to find jobs. Many critics felt the experiment itself was flawed from the beginning and Ehrenreich would have done better to simply interview people who really are living in the way she pretended to live.