Freddie Mac believes its has learned valuable lessons from its experience in the subprime market. And the government-sponsored enterprise apparently isn’t bashful about sharing that knowledge. A case in point is a recent memo on the art of servicing subprime loans. "Borrowers who have experienced credit difficulties often have challenges that differ from the traditional borrower," Freddie Mac said. "Since they have no place to go for money if expenses arise, credit-challenged borrowers have a