you are required to sign a 2-year "training contract". if you voluntarily leave within the first 12 months, you pay the full amount. if you leave 12-24 months, you pay 50% of the amount. after 24 months, you pay nothing.
the contract is being enforced. they (mgt - the pilots and union don't agree with it) are using a national collection agency for enforcing the repayment. i've heard of several pilots being pursued by this collection agency and their attorny. it does go on your credit report as a non-payment.
the other "2-year" issue you may have heard about is a 2-year equipment lock (or seat lock). once assigned to your initial a/c, you are in it for 2 years. however, you can upgrade in that type. also, if pilots are needed in another fleet, they sometimes release seatlocks co-wide to fill those positions.