I think what I find problematic about the events in the Ukraine is not that Russia sent troops into Crimea (as I had stated in an earlier post, Russia has a legitimate interest in protecting its military installations there), but that Russia then sent sent troops into other portions of Crimea prior to any vote of self-determination by Crimeans.
It is uncontroverted that the Crimea has a majority Russian-speaking population. In that respect, it was like large portions of Texas prior to Texas seeking independence from Mexico. However, Texans first obtained independence, then sought to join the United States. Here, Crimean "independence" has the appearance of being imposed from Russia. The situation would have been more palatable if Russia had stayed aloof from the situation, at least until after there was a plebiscite in Crimea approving independence from the rest of the Ukraine.
Some of you may be aghast at the thought of a people voluntarily joining the Russian Federation. But we are not talking about Stalinist Russia. Whatever problems there are in Russia, it appears from what I've read to be exceeded by the corruption and economic problems in Ukraine. And, there is a natural desire to associate with one's own. Forcing two peoples together that don't want to be together rarely leads to good results.
I would note that there has not been violence between the military forces in Crimea. In other words, this has not turned into Hungary and the Soviet intervention there. And, it appears that after talking to German Chancellor Merkl, Pres. Putin has pulled back troops from the Ukrainian border.