Sadly, this sounds like collateral damage in the Russia - Ukraine conflict.
Interesting take from the Ukraine military:
A statement from the Foreign Ministry in Kiev said the plane had been "shot down."
"According to the General Staff of Ukrainian Armed Forces, the airplane was shot down by the Russian Buk missile system as the liner was flying at an altitude of 10,000 meters [33,000 feet]," the statement added. "Ukraine has no long-range air defense missile systems in this area. The plane was shot down, because the Russian air defense systems was affording protection to Russian mercenaries and terrorists in this area. Ukraine will present the evidence of Russian military involvement into the Boeing crash."
http://abcnews.go.com/International/...ry?id=24599558
If its true that the Ukraine military has no ground to air assets in the area - an assertion that might be tricky to confirm - than that leaves the Russians. Also interesting are reports that the black box has been found and is on its way to ... Moscow?!