Sex addiction: It's a phrase many people take as a joke.Some may remember the old "Cheers" episode in which Sam, the lothario bartender, attends a Sexaholics Anonymous meeting to cure himself of his womanizing ways. He leaves the meeting with several dates."I've heard people say, "Oh, sex addiction? I'd take that any day!' " said psychologist Jeanne Pettijohn of Overland Park, Kan.But Pettijohn knows it's no joke.She knows because for the past 10 years, her practice — once dedicated to treating alcohol and drug addiction — has burgeoned with men and women whose careers, marriages and entire lives are being...