I'd like to point out that not all job offers that fail to appear are the fault of the summer associate.
A law firm my friend worked at (a 40-attorney insurance defense shop) did not offer jobs to two of the four summer associates. They did this because the firm's finances had taken a downturn. The senior partner of the firm assured him that his not receiving an offer was not a reflection on his performance. To further this idea, the senior partner penned an outstanding letter of recommendation for him.
Nontheless it is difficult for my friend to explain this scenario without sounding like sour grapes. What would you recommend?