Syria

So why hasn't the West intervened in Syria? Well there are a lot of different reason but the biggest in probably fear. Not fear of what Syria could do to them but fear of the chaos that could, and probably would, erupt all over the area. Add tot hat the rather serious logistical problems and the simple fact that more nations are interested in continued stability than they are in keeping some protesters alive and you have a potent mix of "Stay Away!"

Libya was easy. It had a pretty dysfunctional military, had a huge coast line and most of the targets you had to hit we right there along the coast. Syria on the other had has a military that is relatively well equipped and well trained. Their Air Force and Air Defense system is set up to defend against Israel so it clearly is as good as they can make it. Now this doesn't mean that the West, or more specifically the US, couldn't flatten it. They/We could but it would take an air campaign the equivalent of those at the beginning of Gulf Wars I and II. Massive round the clock attacks. (although this would be simplified somewhat by the new generations of drones which could be used against Air Defense sites) The problem with this of course would be where do you stage the attacks from? The Mediterranean of course is a good site but Syria doesn't have a huge coast so you would need to either overfly Lebanon or stay in Syrian Airspace for the whole raid. And I doubt Lebanon would grant overflight permission. Hezbollah would prevent them allowing it even if they wanted to. Similarly I don't think the Saudis or the Iraqis would let us stage or overfly for bombing missions. The obvious place to launch from and clearly the politically impossible place is Israel. We would not want Israel involved at all for any reason. For that same reason of course, if we attacked Syria, I would not be at all surprised to see Syria attack Israel. We don't want the specter of Zionism over the fight and they need would need it. Hezbollah and Hamas would probably jump into an Israel fight too. then, lat but far from least we have Iran which I seriously doubt would sit peacefully by while we bombed their Arab ally/client into submission.
A whole world of hurt for everyone is just sitting there waiting to get opened up.
Then of course we have what could happen after the bombing, Syria is fractured politically, religiously and socially like Iraq and Lebanon are. The odds of vicious sectarian conflict breaking out after the collapse of the Assad regime are huge. Nearly certain in my opinion.

So intervention is just a huge ugly hole waiting to get ripped in the middle east.
Unfortunately, not intervening isn't a whole lot better. Assad has failed where his father succeeded in crushing anti government forces. His problems seem to keep growing each and every day so those chances of sectarian warfare keep looming larger and larger in the future.
The only intervention that might,a nd allow me to emphasis the MIGHT there, succeed would be if say Turkey and Saudi Arabia/Jordan did the whole thing on their own. To make that work they would have to bride the Syrian Military into throwing Assad under the bus. And even then, we have the Iranian/Hezbollah wild card waiting to screw things up. so I don't see any such thing happening.

In fact, I think it looks real bad there for everyone. There will be no winners in this mess unless we (being the world as a whole) get really lucky