What if the driveway cracks?
If your concrete was jointed properly, cracks are unlikely to be a problem. Think of joints as "planned" cracks that allow the concrete to expand and contract, minimizing any chance for random cracking.
Although joints will control cracking in most cases, even properly jointed concrete can crack in places other than the joints. Most of these random cracks are simply unplanned joints and won't impact the long-term service and durability of your driveway. But they can detract from the appearance. If you're concerned about random cracking, ask your contractor what measures he will take to prevent it and what his policy is about fixing any random cracking that does occur.