The shorter Steve Cook: Bashar al-Assad is massacring his own people, but the West doesn't want to intervene because they think he'll fall soon enough. He won't though, and while intervening is difficult, it's not as difficult as the conventional wisdom holds. It may have the added bonus fo the US to undermine Iran's regional position. That being said, post-Assad Syria might be a disaster.
The shorter Marc Lynch: Bashar al-Assad is massacring his own people, but a massacre is not enough ground to strike against a country, even if it may be part of the ground. Any form of military intervention, such as a no-fly zone, would quickly grow into something complicated that would draw the West in further. The Syrian opposition is not yet strong enough to provide a real alternative to the regime anyway. Beef up sanctions and go to the ICC first to isolate the regime further and provide a legal basis for more down the road.
My short take: I am always againt military intervention, humanitarian or otherwise, because of the experience of Iraq and because I believe in national sovereignty as the cornerstone of democracy and in respecting international law. I do not see Russia and China giving a go-ahead for UN-sanctioned intervention, nor do I see Arab unity over intervention in this case. That being said, we must be realistic about Syria: the conflict is likely to perdure and will probably draw in its neighbors – Turkey, Iran, Iraq, Lebanon, Israel. In other words, it is likely to internationalize. These countries (and in the case of Lebanon and Iraq, others working through them) may want to back a particular faction, or quarantine the conflict (which will have an impact on the belligerents, of course). What's more, fighters from those countries may very well want to join one side or the other (there have already been rumors of Iranians joining in on the regime side). In other words, foreign intervention will be a reality sooner or later. I'd rather it'd be done by Syria's neighbors then the West, even if that means it will be bloodier or even if it leads to Assad staying in power. Quite simply, it's none of our business.