At a protest last year at New York University, students called attention to their mounting debt by wearing T-shirts with the amount they owed scribbled across the front — $90,000, $75,000, $20,000. “I couldn’t believe the accumulated wealth they represent — for our industry,” the consultant, Jerry Ashton, wrote in a column for a trade publication, InsideARM.com. “It was lip-smacking.” Though Mr. Ashton says his column was meant to be ironic, it nonetheless highlighted undeniable truths: many borrowers are struggling to pay off their student loans, and the debt collection industry is cashing in. As the number of people taking...