I'm a little worried that this is introducing a new vector for spam. I have already been getting spam through invites (where they get auto-added to my calendar even before I have a chance to see what they are).

Frankly, I want my calendar to be a private calendar. I don't want to share it, or receive invites through it, or auto-add events just because I got an email. I'm still happy to have the sync capability, because I use a smartphone, but aside from that I really have no use cases which require my calendar to be online at all.

Admittedly, this may just be a case where Google's interests are not aligned with my own. If so, are there (real, viable) alternatives?