That's what I mean, 64 degrees isn't the end of the world. And for the few hours of the night an infant sleeps, it's the same issue as if the power/gas were to go out.

That might be, but I wouldn't use the word "dangerous" to describe the effects of a thermostat not working. It's the same as when the power goes out. Obviously, no one is leaving their baby alone for hours and hours and hours while the temp actually gets to freezing level such that it would harm the baby, so what is so dangerous about it?

I can see the harm in frozen pipes and whatnot, but you take the same risk when dealing with other systems, such as other thermostats or power or the furnace itself. However, if it is known that Nest devices fail when the internet fails, then that is Nest's responsibility to advertise that to users.