Three Five quick thoughts on the Moscow subway bombing:
1) Who gets the blame? As Clifford Levy points out in the NYT, "Mr. Putin built his reputation in part on his success at suppressing terrorism, so the attacks could be considered a challenge to his stature." On the other hand, one could see Putin trying to shift the blame onto Russian president Dmitri Medvedev or Moscow mayor Yuri Luzhkov as a way to thwart future rivals. On the other hand, a lot of Russians are already unhappy with the government, and diversionary tactics might not work this time.
2) Is there an international dimension? Russia's neighbors in the Caucasus and Central Asia, along with the United States and China, are praying right now that the suicide bombers were entirely domestic in origin and execution. If there was an international link, one could easily envision nightmare scenarios about Russia's international response.
3) How screwed is the North Caucasus? They were already pretty screwed because of the Putin administration's attempts to crack down on secessionist groups in the region. I seriously doubt that this attack is going to cause Russian leaders to rethink their strategy. If anything, a doubling-down approach is the likely outcome.
4) Hey, Europe might be relevant again!! The New York Times' Steve Erlanger reported on the latest Brussels Forum meeting, at which European security and foreign policy officials kept saying, "we're relevant!!" Given that the highest-ranking U.S. attendee was an Assistant Secretary of State, I'm pretty sure that U.S. officials didn't think that dog would hunt ex ante. A Russia ready to lash out, however, is guaranteed to force more transatlantic consultations.
5) Obama's counter-terrorism policies don't look so bad in comparison. This is unfair -- the process matters just as much as the outcome, and it might be that the Obama administration is just luckier than the Medvedev/Putin administration. Still, the comparison will be made (though Michelle Malkin attempts to link the attacks to Obama's weaknesses on counterterrorism).