Well since I've seen various posts and replies which contain various misunderstandings I've decided to throw my two cents into this jar as well.
First. Israel.
The general consensus in Israeli public (and strategic) opinion is that although Assad was considered an enemy, under his regime our Northeastern front has been the most stable of all our fronts, for absolute decades. Under the Syrian regime, there is no recollection of any significant violence coming on the side of the Syrian border and spilling into the Israeli side of the Golan Heights. Furthermore, to those brainwashed members who speak of Israel's interest in this conflict, be mindful that the removal of Assad certainly is not perceived as a strategic desire in general, and is even seen as counterproductive. The border with Syria today is unstable in ways which it hasn't been for possibly over 40 years. Violence from the fighting between rebels and Syrian troops is spilling into Israel, and possibly hundreds of Syrians have been treated in Israeli hospitals in the area, as they flee the violence.
In addition, it is interesting to note that it was America which has torpedoed Israel's effort to establish peace negotiations with Assad several years ago.
When it comes to Obama's (and others) so called red line of using chemical attacks, the rationale behind such dramatic declarations reek of sheer lack ability to address the broader picture. Some estimates put the death toll in the Syrian civil war at well over 100,000, perhaps even 120,000. Is the president of America suggesting that while over a hundred thousands of people have already been slaughtered, and millions have turned into homeless refugees, his red line is the death of a couple of hundreds more? those who happened to die from Sarin gas? That logic stinks of strategic cowardice, and complacency with the brutality of the Syrian regime which has de facto been unleashing a genocide for over 2 years now.
Intervention wise, there is no elegant solution, and the whole stuttering of nations like the UK, France, and most of all the US exemplifies their hesitations, doubts, and even lack of faith in their own capabilities (including the capability to hold a public front back home).
The cold, and strategic side of my mind says a simple thing. Neither the rebels or Assad's Syrian forces seem to show humane goals in general. Both sides commit atrocities that defy logic. And both contain anti-Western, anti democratic, and in many cases radical elements.
Let these two sides weaken each other. This Sunni-Shia rift is reaching a climax now on the Syrian (and also Lebanese) theatre. Not only does this conflict weaken various hostile parties, but this is a chance to give dozens of Islamic states, which have been involved in severe tensions and proxy wars with each other a chance to begin resolving, or at least addressing this deeply rooted internal conflict inside the Muslim world, which by now has caused the lost millions of lives, and millions of refugees in only a mater of several decades.
If of course, the west and Sunni states decide that they can not stand idly as a genocide is being committed inside Syria, then the optimal strategy seems to be a more active support of the Syrian opposition, and as Sterling said earlier: Softening the targets, paving the way for a more successful resistance which is going to be won, not by deploying American troops, but by the Syrian opposition forces themselves.
