Why not do it yourself over the LAN? Seriously, I dont see any point in having home data get sent to some scummy third party.

I have a few of these "smart" devices in my home, and they are assigned to an IP block that has absolutely no internet access. They have to be controlled internally, and are not allowed to phone home.

One of my next projects will be an open-source Alexa-like that runs completely in the LAN (unless you specifically ask for things like the weather).

This already exists to some extent: https://mycroft.ai/

Nest hasn't been that impressive to me, but they're better than a lot of other home automation/security providers, including the one who completely mishandled a security disclosure I made a couple of months ago. The issue was remedied, but it was very unprofessional, and I didn't bother doing digging deep. I am certain there are many other simple security issues with that platform, just waiting for someone to decide that they want to play a game with $IMPORTANT_PERSON_X's home locks.

It's definitely wise to think twice before making your home's basic functionality, like allowing the owner to unlock doors, depend on systems that require an internet connection.

Will you share the bad company so I can avoid it?

While I'd like to, since I haven't gotten into the nitty-gritty, I don't want to name and shame based on presumptions, even if I have an isolated data point that supports them.

I would just say to be careful whose devices you use. Do your research and understand that you're implicating not just your privacy, but your physical security, when you put remotely-controllable locks, blinds, etc., in your home. That's a position of high trust, and most home automation providers (possibly including Nest, but they're by no means the worst) aren't worthy of it.