In the last couple of years, Linden Lab has grown from around 50 people to (we are told) around 250 people. It is a growth stage of companies that most do not survive, as usually they do something lethally boneheaded in the process.
Another stage that many companies do not survive is their first change of CEO. It is a massive change for the company's table of organization, reporting chains and corporate culture. The first CEO change generally sees a large staff turnover.
That's what usually happens, anyway. While we're not predicting sudden death for Linden Lab, they're getting their first new CEO today.