I was never fond of conspiracy theories. Not because people don’t conspire, far from it. But because in politics, people are not that shrewd and are not endowed with awareness of the long-term. In light of this, a couple of points so as to make sure everybody agrees on this:
1- It is the ‘ruling majority’ government (specifically the Hariri camp) that gave the possibility (directly or tacitly) for Fatah Al Islam to develop. As would say Al Haqid, Fatah al Islam is a Lebanese political actor, or is a product of the Lebanese political system. It is also the result of the corruptive and incompetent practice of post-Syria-withdrawal Lebanon government.
2- The US administration may have overseen or even financed the formation of the such groups, even if today it is possible that they cannot control what they started (recent history is replete with such examples from Afghanistan).
3- It is much less likely that the Syrians are behind the whole thing in the sense that Syria would not want to jeopardize the Lebanese army (one of its only remaining ally), and neither would want to put Hizbullah in an awkward position (which is clearly the case today).
4- Both actors can benefit though from likely future developments, although the US will definitely have a much more important role to play (maybe military) in Lebanon. Syria is to remain on the defensive trying to collect pieces of what is left from the US elephant-like advancement in the Middle East.