The Justice Department is stepping up its investigation into hiring practices at some of America's biggest companies, including Google Inc., Intel Corp., and Apple Inc. The inquiry is focused on whether companies, particularly in the technology sector, have agreed not to recruit each others' employees in ways that violate antitrust law. "In the long run, this is going to distort and depress the incentives for people to actually develop the talents and skills that are useful in this market," said Salil Mehra, a Temple University law professor who formerly worked in the Justice Department's antitrust division.