Google has a variety of mechanisms that can be used to effectively get rid of people without them understanding why. For instance they allow anyone to give feedback on anyone else during promo cases which can sink promotions or entire careers, and which isn't merely anonymous but completely confidential. That's been mentioned elsewhere on this thread. The result is that people can appear to be doing very well with glowing feedback, happy managers, successful projects and then their career suddenly goes off the rails without that person ever being told why, for no better reason than a single person didn't like them. This blog post gives off strong vibes of this sort of thing, given the vagueness about why he had to leave.

This problem interacts badly with another problem Google has: it started with a culture of extreme internal openness compared to most organizations. For example almost all internal mailing lists were open, almost all internal code was open to all engineers, people were encouraged to send feedback and resolve problems directly across teams instead of always going through management and so on. Hence the mono-repo so large they had to reimplement Perforce to keep it running.

In an environment where everyone is culturally very similar, has a lot of experience of the world outside of Google to keep them grounded, a clear and motivating goal and minimal politics, this can just about work. It worked OK for the first 6-7 years or so I was there. It ... stopped working. The combination of very open communication, an increasingly radicalized workforce (due to their heavy dependence post 2010 on recruiting new grads to keep the hiring pipelines full), and formal systems for secretly sinking people's careers = a lot of very messy problems in which loyal workers get screwed.

The vast majority never talk about it in public, at least not under their own name, but there are a lot of Evans out there.