Adam Chapman (Kingsley Napley, Partner and Head of Public Law Department) described the CJEU's approach as "maximalist, and probably to many people a counter-intuitive". "The obvious and immediate consequence of the two [on Facebook pages and D2D note-keeping] decisions is that a considerable number of organisations which, up until now, had not considered themselves to be joint data controllers will have to review that assessment", he added.
Another interesting legal blogs:
CJEU rules on joint controllership - what does this mean for companies?