That's because some states tax forgiven debt as income, which means borrowers who are still paying down student loans could owe taxes on as much as $10,000 or even $20,000 that was taken off their bill. In Mississippi, Minnesota, Wisconsin, Arkansas and North Carolina, forgiven student loans will be subject to state income taxes unless they change their laws to conform with a federal tax exemption for student loans, according to a tally by the Tax Foundation, a Washington, D.C.-based think tank.

That dismays Cathy Newman, a Louisiana State University graduate who just took a job teaching freshman biology at the University of Southern Mississippi in Hattiesburg. She figures she could end up owing a few hundred dollars of money that she could have kept had she stayed in Louisiana.

Newman said she can come up with the cash because she has a good job, but she knows of a lot of other borrowers who will still be stuck in difficult financial positions even with their loans forgiven.

"If they stay in the state, they could end up with a pretty hefty tax burden if things don't change," Newman said. "I won't be happy if I have to do it. I can do it. But a lot of people can't."