Can You Be Sued for Written Employee Recommendations?

ServiusCensus asks: "I have been asked to provide a written rather than the more normal verbal reference for a someone I used to work with. Verbal references seem to be the norm, they work well because people are more willing to tell the truth informally than they are to write it down. I want to know what problems I might get into if I recommend someone but they turn out to be a bad match for the company? I don't want some lawyer to come looking for me one dark night."