People have been fighting wars over the Crimea for centuries. I believe it is on record as being one of the most contentious spots in the history of the European Continent. Throw in tribal loyalties, long standing historical grudge matches, violent games of "top this" and long running oppression of and retaliatory violence from a large ethnic Muslim population, you have a perpetual powder keg on your hands.
Again, the violence in Kiev last week is not uncommon in this entire region, and has not been uncommon for Centuries. The only difference now is that the military police have better weapons, and everyone with a camera is recording the violence and posting it near live on the internet. Under the Soviets this kind of thing would have been put down immediately with overwhelming force, and nobody outside of Kiev would have known anything about it.