Does content marketing work just on your own sites?

I've been considering the question recently about where it is possible to carry out content marketing. Or to turn this into an actual question: "Can content marketing activity only be done on your own sites?"

My initial answer to this question was a clear "Yes, all CM activity needs to be done on your own sites". Or to put it into more 'consultant speak'... Content Marketing activity only utilises 'Owned' digital sources and does not involve 'Earned' or 'Paid' ones.
Note: Owned online properties are those where you have the ownership and means to change the content. Company brand sites, eCommerce portals, brochureware sites, Facebook pages (where your organisation manages what is posted there) and campaign microsites are all included in this definition.

However, whilst writing a blog post to this effect and therefore thinking it through in more detail... I realised that this initial response might not the correct one. Most content marketing efforts do start on your own sites, but ignoring the paid and earned sources means you are missing out on a significant amount of content marketing potential.

To try and explain my thinking, I've pulled the following quick diagram together:

This diagram tries to explain the following:

1. Your owned properties can be used to push content into the earned space. E.g. Via the use of social sharing tools you can extend the reach and impact of your content.
2. Your earned media can help shape influence and therefore build traffic to your owned media.
3. Paid media can help to directly bring traffic to your site.

This might be presented in some other way that conveys value or link juice more, so as-always I reserve the right to revisit this diagram in some other blog post.