Well, Fearless Leader has won the referendum in Crimea with 95% of the vote, so back to
the USSR Russia Crimea goes. One can determine the trustworthiness of that vote by recalling that 36% of the population of Crimea is ethnic Ukranian or Crimean Tatar, neither group having much love for the Rodina.
If Putin were going to stop with Crimea that would not disturb me much. Sevastopol has always been the main naval base of the Russian Black Sea fleet. With 58% of the population of the Crimea being ethnic Russian, the Russians clearly made a major mistake in allowing it to become part of the Ukraine and Russia was never going to allow a hostile Ukraine to keep it.
The problem is that Putin is unlikely to stop there. In Obama he realizes he is confronting the weakest, and most feckless, President the United States has had since James Buchanan. He views this as an opportune time for him to recreate the old Soviet Union as much as he can. Next up is likely to be Eastern Ukraine.
When the old Soviet Union collapsed, plenty of ethnic Russians were left in newly independent states. Putin views these as an excuse to expand the current Russian borders. Welcome to Cold War II, with Obama and his Secretary of State John F. Kerry working ceaselessly to make the world safe for “former” KGB thugs dreaming of empire.