Relatively minor from the perspective that the actual information which will leak from a Nest camera isn't really that unique. And as a network device, it's fairly simple to isolate and secure. The video a doorbell camera shoots is generally of "in view" public space, already visible to any camera. Your identity is already likely tied to the installation address where you've paid for the account with your credit card, which is also probably tied to that same address. If these things are not true, then you should obviously defer to your individual threat profile and disregard what I say.

The worst part of it is that these doorbell cameras could provide a state actor with a daily face shot database, but if you control it, then it can also be an adversarial source to that end.

But "minor" for me, is different from "minor" for you. For me, petty crime, and maybe some local cops with beef are a much bigger deal than hiding from the feds. That's my whole point here. Know your own threat profile. If officer Barbrady kicks down your door and violates your rights, he's going to take your local video server, but he's much less likely to get access to some random silicon valley colo farm. Don't fear the cloud, understand how to use it as a tool within your own threat profile.