Answers

Check the frequency and depths of the control joints/sawcuts they installed for your driveway.  They all are subject to industry standards.  A driveway that is 4" thick should have control joint/sawcut depths of 1" deep (24% of the total thickness) and not more than 12 feet apart.  Check these out and if he has installed the concrete within these limits then it is difficult to warrant random cracks that appear.