"There is a
second point that is seldom considered. Suppose the Assad government does fall,
this is meant to be a damaging blow for Iran, deprived of its one Arab ally. It
is meant also to weaken Hezbollah, the Shia guerrilla movement in Lebanon. Both
these things might happen. But keep in mind that the Assad regime is most likely
to be succeeded by general anarchy in Syria, or at best a weak government. Going
by the experience of Iraq and Lebanon, the Iranians and Hezbollah are better
than the US at fishing in troubled waters. Complicated situations are ideal for
exploitation by the Iranians, with their taste for devious political
games." (thanks Ali)