NOT LONG AGO, I was having lunch with one of the best-known players in the entertainment industry when the conversation turned to the rumors du jour about top management shifts. My luncheon companion suddenly displayed a pensive frown. “Why does your newspaper keep referring to people like me as ‘executives’?” he asked. “You should call us corporate mercenaries, because that’s exactly what we are.”His remarks came to mind when I heard of the abrupt departure of Jeff Sagansky from Sony last week. The announcement was made almost matter-of-factly, as though it were something to be expected. Yet Sagansky had been associated with the company for some 13 years, most recently as co-president. The reason he was leaving, it was explained, was that Sony had assigned him certain key responsibilities for its foreign business planning, then had changed its mind. OK, that’s clear enough. But what does it mean? How can a giant corporation simply “change its mind” when dealing with one of its stalwart managers? Then I remembered the admonition over lunch. Corporations should be free to deal as they wish with their mercenaries, I realized. And vice versa. That’s the way the system works. “Of course, there are certain things that are being sacrificed in the new mercenary corporate culture,” my luncheon companion had explained. “Such as loyalty. There is no such thing as a loyal mercenary.” It’s hard to identify the moment in history when top executives became career mercenaries. At CBS, for example, the change came during the Laurence Tisch epoch. I remember being told by one of Tisch’s top aides that he never got to know any of his senior managers on a personal level because he intended to fire most of them. Needless to say, Tisch did not inspire great loyalty. MARTIN DAVIS, who ruled Paramount for a decade, had a similar disdain for his troops. At one moment during his reign, he employed Michael Eisner, Barry Diller and Jeffrey Katzenberg. He turned them all into mercenaries, and all fled to other companies. Around Hollywood, the mercenary culture is now firmly established. Most movie and TV executives assume that they will often shift employers in building their careers. Hence their focus is purely short-term: A search for instant hits to buttress quarterly earnings. Ironically, it is Warner Bros., the studio now undergoing the greatest stress , that represents the last bastion of stability. Until recently, that is. When Chris Pula came in as president of domestic theatrical marketing, he found himself attending meeting after meeting where he was the lone newcomer — everyone else had been a Warner employee for two decades. But when one Warners picture after another started bombing, it was the newcomer, Pula, who was promptly pitched overboard. In Hollywood, of course, this was the time of year when, in times past, corporate loyalty always came to the fore. It was a given that everyone voted for the Oscar nominees representing his studio. The publicity department reminded everyone of this obligation, not very gently. An Oscar vote was a condition of employment. None of this caused much distress, however, because MGM employees really did root for their pictures, as did those at Paramount and Warners. As much as everyone at Columbia hated mean old Harry Cohn, most nonetheless wanted Columbia pictures to win. THIS IS HARDLY THE CASE today. Most studio employees identify with the rent-a-guards manning the studio gates — they know they’re here today, gone tomorrow. And they cast their votes accordingly. Some denizens of the showbiz capital miss the old days when loyalty counted for something. It was nice to know that you wouldn’t be canned if you screwed up — you might actually get a second chance. Mercenaries aren’t nostalgic people, however. Jeff Sagansky will move on to a better job. Another mercenary will take his place. That’s the way it is in the New Hollywood.