Jonathan Heiliger, top Facebook exec, may leaveWill the last tech executive to leave Facebook please turn off the lights at the datacenter? We hear Jonathan Heiliger, Facebook's operations VP charged with running the social network's expansive server network, has been interviewing for other jobs. He just completed a year at the company, which is usually when employees' stock-and-options packages begin to vest. Odd: We thought Heiliger might be happier at the company with the appointment of Marc Andreessen to Facebook's board.Heiliger previously worked for Andreessen at Opsware. One would think the chrome-domed entrepreneur, now chairman of Ning, would prove a powerful ally in the fierce political battles that have roiled Facebook since the appointment of Sheryl Sandberg, a Beltway insider turned Internet executive, as COO. Nothing's certain, and Heiliger may well stay. But for him to be so unhappy as to openly entertain job offers? The social network's executive suite seems to be coming unplugged.