I tend to agree, and it's also worth pointing out that calendars in O365 work similarly. We have them configured to be public by default because it makes it mu

I tend to agree, and it's also worth pointing out that calendars in O365 work similarly. We have them configured to be public by default because it makes it much easier to book meetings, particularly when you need to find a slot that works for several people. With that being said it does assume that you have the common-sense to make appointments that should be private, private. I tend to do this for any personal matters, along with any meetings that involve discussing sensitive work-related matters. (I also use private appointments to ensure I get a lunch break if a day is looking particularly full of meetings. If I don't eat something at lunchtime I tend to be bad-tempered in the afternoon, which doesn't really help anyone.) Worth pointing out that we've clearly communicated that calendars are public by default, which hopefully helps people to know they need to make appointments explicitly private if that's what they want.