The NYT Sunday Review has a succinct article, with many good quotes, for example Will McCants:
Al Qaeda is kind of a ready-made kit now..It is a portable ideology that is entirely fleshed out, with its own symbols and ways of mobilizing people and money to the cause. In many ways, you don’t have to join the actual organization anymore to get those benefits.
The penultimate sentence:
But while counterterrorism can be effective in stopping specific threats, depriving militant groups of the unstable environments where they flourish and organize is much harder.
The last sentence reflects a focus on the Middle East, when IMHO it ignores the sustenance provided by some within stable, governed territory (KSA, Gulf sheikhdoms etc) for militancy elsewhere. The Yemen has been a nearby "sideshow" for years, then there is the 'sore" of Iraq and now Syria. None of them appear to mobilise beyond a small militant minority, which we all too often overlook in our fear.

What you are seeing in the Middle East is a problem of militancy combined with ungoverned territory,....That is the real problem, not which groups belong to Al Qaeda and how can we get rid of them.
Link:http://www.nytimes.com/2014/01/26/su...aeda.html?_r=0