But the "proven bad" technology you're talking about here is just incorporating any third party content in your site. Obviously that is a security risk if the third party isn't perfect about policing what they host.

On the other hand, billions of resources are served in that way every day, and the web is a much better place for it. Only a tiny fraction of those third party resources are hostile, and most of the ones that are will be closed down rapidly by the third party service themselves once discovered.

So is this really in "proven bad", "known-risky" territory, or are we actually talking about "very rare" dangers and a lot of hyperbole here?