Allan Mayer, who developed the entertainment practice for Sitrick and Company after writing a book with the boss, is leaving to start his own firm, Anne Thompson reports at her Hollywood Reporter blog. She says that another senior executive, Kelly Mullens, will leave too and that Mayer is likely to continue advising Steven Spielberg and Brian Grazer. Recently promoted to managing director, Mayer came to Sitrick after serving as founding editor at Buzz Magazine and stints at Newsweek and the Wall Street Journal. Thompson speculates that Steve Oney's profile of Sitrick in the July issue of Los Angeles Magazine stuck in Mayer's craw. Over the weekend, LA Observed broke the news that former Wall Street Journal columnist John Lippman is joining Sitrick.