It's actually a fantastic business model if you care more about profits than ethics, and it seems like Facebook wants a piece of the living room surveillance pie that Smart TVs/Alexa/Google Nest have been enjoying these last few years. It's a shrewd business move on Facebook's part; think of the things people discuss and do in their living rooms and the additional data they will end up giving Facebook.
I get that. But the fact remains that it is a business model, whether we like it or not, and as we've seen it can be very profitable. Until laws catch up, there will always be companies like Facebook that are devoid of ethics and will abuse surveillance technology to enrich themselves.
Is is a healthy business model for a society? I think most people would say no to that.