Big Buyer Taking Media In House… Trend or Exception?

Land Rover is taking its advertising “in-house” via an in-house agency. Is this a trend?  Increasingly with technology make it really easy to buy and sell audience and media online, we are seeing more clients take control of their marketing spend and execution, which is further disrupting the agency business model.  Is this a good thing or a bad thing?   What mistakes are they likely to make when executing themselves?  What do the agencies thing?  Feedback and comments welcome.