The battle over custom content just keeps heating up.

The agencies have the creative track records and talent, but the audiences belongs to publishers. And publishers have been building in-house production teams that can increasingly handle agency services.

But now an agency has gone ahead and bought a publisher of its own.  

So the question grows, how durable are the relationships between marketers, agencies and publishers? And an even bigger one looms: Just how much room is there in the custom content space?