NEW YORK (AdAge.com) — Ben Silverman is out after a two-year stint as co-chairman of NBC Entertainment, where he attempted to revive the fourth-place network with a mix of reality shows and nostalgia, like a failed remake of "Knight Rider." The former William Morris agent, who came to NBC in 2007 as the producing wunderkind behind "The Office" and "Biggest Loser," is going back into business with Barry Diller, the InterActiveCorp CEO and former Fox network chairman who invested in Mr. Silverman's production company, Reveille.