You're right, but a guest account won't allow you to use Google apps - a key part of using ChromeBooks. But more importantly, why should you have to use a guest account in the first place in order to avoid sending your online activity to Google?

I know many posters here have no qualms about Google tracking their online behaviour, but at the very least I would expect Google to clearly state what they track and record when using ChromeOS. That's not an unreasonable expectation. It's something that Google does not provide.