[dragonwriter]

> It's pretty much the worst PR possible for Russia.

Sometimes military actions are taken for reasons other than PR.

> In fact, the only parties who have anything to gain from the plane going down are Kyiv and the US.

Making civilian air travel perceived as unsafe through the Ukraine (and thus, also, into or out of the Ukraine) increases economic pressure on the Ukrainian government to reach an accommodation with the rebels (the PR downside may overwhelm that advantage, but its not impossible to conceive that the rebels might see it as a net gain.) Its not that uncommon of a reason for rebel/separatist forces to attack civilian transport (air or otherwise), tourist, or other targets.

That's not to say I think that it was intentional -- I think that an accident is, given other incidents in the region, the most obvious explanation. OTOH, its not inconceivable that it could be intentional, and there is a clear potential motive for doing it intentionally.