Date: July 18th, 2012 9:13 PM Author: passionate menage
Very unlikely that it'd be Mossad. Assad was no ally of Israel but neither is the Muslim Brotherhood (Egypt-Israel relations are all fucked up now courtesy of Muslim Brotherhood). Maybe CIA, but I don't think the U.S. cares that deeply besides talking a lot and funneling a few millions to the opposition.
You've got a few decent Sunni states there backing the opposition--Saudi Arabia and Turkey--and al Queda's all anti-Assad too so I'd put my money on a regional effort.