Why are Vladimir Putin’s opponents dying?

Having studied abroad in Russia during college, I have continued to pay attention to the politics in Russia. In the last five years, there is no doubt that control of the nation is being tightened within the Kremlin.
What Putin's plans are for next year after he is supposed to leave office are a mystery. But for now, this fascinating article called Kremlin, Inc. does a great job of running down the status of Russian politics. Worldwide consequences based on the leadership of that nation are certainly at stake.