In reply to WillBroad:
I wonder if it was stopped because they reliably cover defence and security issues that the Clausewitz blog overtly covered in many of the paper's other columns and blogs? For instance Charlemagne has for many years been one of the influential columns for all policy makers dealing with ESDP/CFSP and NATO issues. You might just have to hunt around on the Economist website a bit more to find the same sort of stuff.