I have a 3 yr old house that was new when I moved in. There was also hairline cracks from one end basically to the other and to this day have not gotten any bigger or caused futher problems. Also, they are in a realtively straight line. My house inspector was not concerned. From what I recall, the concrete is expected to crack to a certain extent and the "fault" line was placed in the specific location for that reason. As far as the vertical diplacement, I'm not sure. Best of Luck.