Syria often uses its relationship with Hezbollah to exert influence in Lebanon. It's a strange alliance, and it caused Syria to be close to Iran for a long time.
But Syria and Saudia Arabia recently jointly showed up to Lebanon to make it clear that Hezbollah would have no support during the UN investigation of the 2005 assassination of the Lebanese Prime Minister. According to STRATFOR, it's likely that a number of Hezbollah agents will be thrown to the wolves.
The Saudi-Syrian cooperation has been rare in the past few decades. But that it is starting back up (and that Syria is working with Turkey to try to make peace with Israel) is a sign that Syria is joining a small-but-growing anti-Iranian coalition.
The Iranian-Syrian relationship was always strange. Syria is primarily Sunni Arab; Iran is primarily Shiite Persian. A Saudi-Sryian-Egyptian relationship is much more natural (in the 1960's a Pan-Arab state was discussed, which would include Iraq, as well).
This is good news for the US, which wants enough pressure around Iran to keep it in check. In an Iran versus Israel/US world, the US would struggle. But if Iran is sufficiently isolated, there isn't too much it can do.
The long-term risk, of course, is a Turkish-Arab major coalition. It would start looking like the formidable Ottoman Empire. Subverting such a coalition is the primary reason the US wants Turkey to join the EU.