You R right! I would pose this question to your builder, this usually happens when the dry wall has been around a few years, quite a few, and starts sliding past the nail do to weakening from old age, do to settleing or sometimes moisture. I also think your supposed to use "liquid nails" in conjunction with nails. Maybe your builder cheaped out. I, and most people, use drywall screws, not nails.
This is easily repaired by driving a drywall screw, imagine that, in right next to it (an inch or 2 away), and spakle and sand the nail pop, but could be a big job if there are many.