For example one FB friend follows whitewater racing closely and is constantly posting articles and videos from local websites throughout Europe. I would never get to see this content otherwise.

Sure a lot of people on HN don't like Facebook or don't use Facebook, but about a billion people do. And they do it for a reason: they like it.

The question is what obligation does Facebook have to those people--and to society in general--to avoid fooling or exploiting them. I'd say it is at least "some".