It looks like MH17 with 295 passengers and crew has been shot down over eastern Ukraine near the Russian border.
By the Russians? Unlikely.
By Russian-leaning rebels? possibly with a Russian ground to air missile.
By the Ukrainians? by air-to-air or ground-to-air missiles? Not unthinkable.
In the meantime commercial airlines are now avoiding this airspace as – for example – Thai Airways TG921 and others are just doing. There seem to be many aircraft avoiding the area right now.
TG921 and commercial airlines avoiding eastern Ukraine
Considering the number of commercial aircraft in the area, it is particularly poignant that after MH370, it is another Malaysian airliner which has been shot down. And MH370 itself disappeared due to hostile action.
The k2p blog 
July 17, 2014 at 7:12 pm
Not the separatists. Russians only gave them shoulder held versions that top out at no more than 20k feet. The plane was at 34k. Russian surface to air missiles from a battery have been shooting down Ukrainian planes and helicopters for at least the last week. That is more likely scenario. It is possible a retaliatory strike by Ukrainian forces did this as well. Terrible tragedy.