Bill Roggio's piece in the Long War Journal, "Al-Nusrah Front Imposes Shariah in Eastern Syrian Town" captures, with astute analysis, the success that will lead to failure.
I wont attempt a summary here. His writing is too good for that. You'll have to read it yourself! His parallel analysis of al-Nusrah in Syria and al-Qaeda in Iraq is excellent.
There is a self-delusional component to these terrorist groups that allows them to ignore the real attitudes of the very people they claim to be helping.As al-Nusrah imposes its version of Shariah it heavily impacts the citizens of the towns it occupies. Folks just don't like the cruelty.
Their denial of simple realities (like the disdain that people have for them and the anger they generate against themselves) may serve to self-justify their actions, but it will bring them down in the end. The revulsion that greeted al-Qaeda in Iraq gave birth to the Awakening, which seriously weakened al-Qaeda. That same recognition of the horrors of having al-Nusrah in one's backyard will give rise to Syria's own awakening; hopefully before the terrorists gain any real political power. Inshallah.