The last three companies I've worked for are very big heavy hitting technology industry names and every single one had a policy that employees are not to give interviews and that if anyone asks you questions, you should refer them to the PR department or other relevant division within the company. This is to avoid situations where some random employee says something unintentionally stupid and it gets promoted to the top of all the sites as official company line. Or to prevent things like, you know, everyone claiming that "Wozniak wants to return to Apple, if they ask him!" when he never said any such thing.
Additionally, you're supposed to report anyone suspicious on the campus, whether they're trying to coat-tail into the building after you badge-in or whether they're snooping around outside and asking questions.
Imagine you hire a big pool of people who punch in a bunch of 10 key or flip pages on a book and press "SCAN" on the machine all day and someone comes snooping around to ask questions about a project (the digitizing of books) that is currently in litigation and some random jackass employee mouths off about something they haven't the slightest clue about and now it's headline news on all the tech industry rags?
Anyway, it's not peculiar or unusual practice. Its' very common. And from what I've seen, this is all speculation. And not even by an employee (or journalist). It's all speculation by a guy who was hired by a company who was hired by Google to get some footage who didn't like the racial makeup of the people he saw walking out of the building for a few days and then started to ask questions of employees who don't know him from any other random guy on the campus filming stuff and asking strange questions.
The way the accusation is made and the whole "expose" is presented is just absurd. Almost surreal, it's so silly. I can't help but think of it in the same light as the internet meme from a couple years ago, where some guys used Glenn Beck's techniques against him by starting up the website "glennbeckrapedandmurderedayounggirlin1990.com" and then posted the following:
"This site exists to try and help examine the vicious rumor that Glenn Beck raped and murdered a young girl in 1990. Why won't Glenn Beck deny these allegations?"
Except, in this case, it's "This video exists to try and help examine the vicious rumor that Google is classist and racist and abuses its employees. Why won't Google deny these allegations?"