It would work if we honestly had a leg to stand on,in causing these sites to lose business if they did not play ball.
Sadly bitcoiners are gamblers,traders and darknet users to most of these sites and they do not see much upside in adding a feature that could just create more work for them in the end.
Was thinking about this after I think you read the same thread about the medical website and chewing over the same thought.
We are as a community a little narrow focused by nature due to people wanting to cash in on bitcoin and due to the history of early adopters.
It almost was a good thing at first but now its showing its true teeth and we need to some how expand the field in a more diligent manner.

Dating sites seem like a good spot to hit up but they are really about mining personal data and bitcoin would detract a bit of info collection on that side. Really not sure the best tact but its going to take a huge shift to grow the biosphere of bitcoin to get different people involved.