Unfortunately the linked article is a bit light on content. For one thing, I'd be interested in knowing how they built said network of twitter followers.
http://unbounce.com/content-marketing/checklist-12-things-yo...
Doubly interesting since it's both an example of what they do to attract followers and a guide on the steps they take.
But all those content marketing experts fail to answer this: How do I get those people to listen to my content in the first place?!!
People choose to listen when you provide something useful, on a regular basis, in a channel that they're already paying attention to. Once you've gotten their attention, you can convince some of them to join a new channel for which you have better access, control, and tracking.
It's less about getting the listening than the continuous choice to proving something useful.