Novelist Elias Khoury and historian Fawwaz Traboulsi--two major Lebanese intellectuals--are in New York at the moment and spoke at NYU the night before last. I'm not in any way qualified to analyze the labyrinthine politics of Lebanon, but I'm going to summarize some of the main points made during this talk.
Khoury and Traboulsi said that it is not in Hezbullah's interest to start a civil war, and that Hezbullah knows this; but the movement it started--which has been using the exact same methods as last year's "cedar revolution" to topple the government--has now painted itself into a corner, and Hezbullah's allies (Syria and the party of Christian General Michel Aoun) may be pushing for a war because they have virtually nothing to lose from it.
Khoury referred to "the tragedy of Hezbullah"--that it is "bigger than Lebanon" (a pan-Islamic movement) and "smaller than Lebanon (it only represents one sect within the country and therefore can never take full power). In his analysis, it has long been a Syrian calculation to entrust Lebanon's military resistance to the Israeli occupation (Hezbullah ousted the Israeli after years of fighting in the south) to a group that could not, when victorious, represent the whole country and hope to come to power--Khoury points out that a more widespread, leftists, national resisance movement was decimated by assassinations in the 1980s. Thus in his view Hezbullah is as much a tool of Syrian as of Iran.
Which points to another facet of the situation in Lebanon: the way every group there has an outside backer. It is common-place to speak of Hezbullah as "backed by Iran," but Traboulsi and Khoury were at pains to make clear that the way politics works in Lebanon is that every major player turns to powers outside the country to solidify its position--or is used by powers outside the country to promote their interests (the government is backed by the US, for example, the Sunni community by Saudi Arabia). The connection between Lebanese politics and regional politics is one reason that--seemingly overnight--the main sectarian conflict has become that between Sunni and Shias, not Muslims and Christians. This new divide is one of the many consequences of Iraq.