As with all departure-cultures, some are voluntary and some are involuntary. What seems to be a common theme is that departures actually have the effect of creating further departures further down the ranks for months and years. Former executives and coworkers often recruit out of their former employers. Again, this can take place over a period of years, and long after nonsolicitation clauses expire.

Now that Steve Jobs is not going to be involved in the day-to-day operations at Apple, there is no reason to assume that Apple will just automatically be immune to any brain drain just because it is Apple. The timing of before or after the formal Jobs’ departure announcement is arguable, but it may be easy to argue that the Apple brain drain is already afoot. Tim Cook is supposed to be well-respected and very able to fill the shoes of Steve Jobs. He is also less visible, and many of Apple’s ranks could be taking their talent elsewhere for new challenges.

Apple ranks as #20 on the list of great companies to work for at Glass Door. Many might consider it as a top destination, but companies in tech, web, IT, and media above it on the list are Facebook, Overstock.com (NASDAQ: OSTK), CareerBuilder, Shutterfly (NASDAQ: SFLY), NetApp (NASDAQ: NTAP) and National Instruments (NASDAQ: NATI). The good news is that some 97% of employees approve of CEO Tim Cook. The bad news is that a 97% approval rate may be too high to last.

Ron Johnson, the merchandising guru who is credited for the Apple retail stores, announced his departure in recent months to become CEO of JCPenney (NYSE: JCP). He reportedly turned down the retailer in the years before and he did communicate that he had always wanted to be CEO of a major retailer.

Before the Johnson departure, a key software engineer back to the early Macintosh and even back to the NeXT days left the company. This was Bertrand Serlet, who was referred to as the father of OS X, left “to focus less on products and more on science.”

These departures were before Steve Jobs made his formal departure, but many suspected he was not returning. It also seemed fairly certain that the roles in a post-Jobs Apple were already defined months before Jobs announced his formal resignation as CEO. Neither Johnson nor Serlet were expected to take over as CEO after Steve Jobs left. That is not the real problem though.