Some hairline cracks are normal, regardless of their length. What matters is the depth and width of the cracks. As Jay said, wait a while to see how much more the house settles.
I will warn you, that unless the cracks are bigger than 1/4", the builder probably wont do anything. Maybe he/she will but I wouldn't bet the rent on it.
I finished my basement a few years ago, the house was 4 years old by then. I had cracks. I used a crack filler (available at your local hardware store) on the worst cracks. Then I had a berber installed over an 8-pound pad.