I feel like making up a conspiracy story as ridiculous as the ones the rebels and their Russian backers are spewing. Clearly what happened here is that the Russian mafia is engaging in a shakedown of Malaysia Airlines. MA refused to pay, so they got the rebels to shoot down a Malaysia Airlines plane flying over Ukraine. Alas, this actually makes more sense than the theories Putin and his lackeys are regurgitating, tho it has no more evidence than what they are saying.
How about this one? Ukrainian terrorists told Malaysian Airlines that they'd release the passengers they were holding hostage from flight 370 if Malaysian Airlines would sent a flight of dead bodies to fly repeatedly over the rebel areas that was disguised as a Ukrainian military aircraft so that it would eventually get shot down.
Or alternately, the Ukraine took the plane from flight 370, rebranded it as flight 17, disguised it as their own military aircraft, and killed all of the flight 370 passengers and placed them on the plane.