But they are not just doing this for publicly shared posts. Even posts which are shared privately will appear besides the ad when a person whom you have shared

But they are not just doing this for publicly shared posts. Even posts which are shared privately will appear besides the ad when a person whom you have shared the post with is viewing the ad. That by itself is not a problem. However, to curate the post, somebody from Google would have to read it. Else, they have really good natural language processors.