"Google employees are going to be using Google Calendar for work"
If only there were some way to have multiple accounts, one personal and one corporate.
"If those employees were stalking others at the company by having calendar event change alerts, that's exactly the behavior that Google should be firing people over."
The behavior in itself does not seem problematic; I can think of any number of legitimate use cases for wanting to know when someone is available or perhaps when they're giving an open presentation on an interesting topic. It appears possible that the employees in question abused this capability, but I have to wonder if Google would have cared if the employees weren't using it to expose behavior they thought was ethically questionable. Google certainly has form in covering up dodgy stalking behavior (e.g. managers stalking employees "romantically"), so ask yourself why these four got the boot.