We are in the process of deprecating some old Page Insights. We announced this in a number of forums, but failed to outline this change in our Platform Roadmap per our breaking change policy. Our apologies. You can find a full list of the Insights to be deprecated from the Insights documentation. These Insights will be completely removed from API on Feb 15th 2012. Please make all necessary updates as soon as possible so that you can transition smoothly.