Glad I read this article! On Saturday I found I couldn't access my Gmail on my mobile without logging back in and then later, noticed, on my laptop, that my Google Drive Sync was off, because, it turned out, I had to sign back in there too. Then Google sent me an email to my secondary email account telling me I'd logged in from a new machine (yes, I had just logged in, but no, it's not a new machine).
I didn't think anything of it, until my eldest daughter complained on Sunday that she hadn't been able to access her Gmail. I got her to reboot her phone and it too asked her to login to Gmail and then sent me an email (I'm her backup email account) saying she'd logged in from a new device...
Very odd and I'm not sure I like the fact that Google sit between saying nothing's going on, or they don't think anything is going on.