I think the West is going to end up looking a bit silly in this. Russia has morale authority here since Yanukovych invited them in. The Russians have come in with a small force appropriate to the mission of protecting civilians and stabilising the Crimea.
On the other hand, we are trying to prop up a mob who ousted a democratically elected President, broadcasting laughable mob propaganda that Russia is threatening to attack, and now threatening sanctions that will affect our own economies as much as Russia's.
We'd be better off agreeing to help the Russians sort it out. At least we would then have some say in the future shape of Ukraine.