An interesting backgrounder:
Hezbollah’s open intervention in its neighbour’s civil war has from the outset posed many questions and provoked not a little anxiety. What exactly are Hezbollah’s aims in Syria? In light of the reprisals that have been conducted by its Syrian foes and their sympathizers in areas sympathetic to the group or under its control, doesn’t it have more to lose than to gain? Finally, and in particular, does Hezbollah risk losing its popular base and its pre-eminence on the national level in Lebanon?
Link:http://www.lobelog.com/hezbollah-win...at-what-price/

There is an odd passage - my emphasis, perhaps an exaggeration:
..the first units were members of local self-defense forces that formed spontaneously in the increasingly conflicted zone along the border. Having never been precisely demarcated, the border between northeast Lebanon and Syria constitutes a large area that is home to some 30 villages actually inhabited by Lebanese — mainly Shiite — citizens, all of whom, however, are subject to Syrian sovereignty. Given their sectarian character, these villages were targeted early on by Sunni jihadi groups linked to the opposition.