From TIME.com:
Russia’s escalating intervention in Ukraine once again confronts Barack Obama with a foreign policy crisis over which his options are painfully limited, forcing him into a reactive posture that relies on tough, but largely hollow rhetoric.
Appearing on short notice in the White House briefing room yesterday, Obama warned Russian president Vladimir Putin that “there will be costs for any military intervention in Ukraine.” Within hours, Putin had requested and received from Russia’s parliament the authority to use force in its western neighbor, whose capital city Kiev saw an uprising against Moscow last month.
Putin appears to have calculated that the benefits of maintaining control of Ukraine’s Crimean peninsula, home to a large ethnic Russian population and a major naval base, would outweigh any costs that Obama and the West can impose.
He’s probably right.