There are very good reasons to wish good things for the revolutionary movement in Ukraine. However, we aren't going to support them openly with any real strength. This is because of logistics. Not the logistical problems identified by Zenpundit -- that is, the ones that pertain to the possibility of fighting in Ukraine. Those problems are real enough, but they aren't the reason.
The real reason is identified correctly by Charles Hoskinson of the Washington Examiner: our logistics in Afghanistan. He obviously has good contacts who understand how the pieces are moved.
Meanwhile, there's also the problem of Afghanistan — the "real war," as Obama, Vice President Joe Biden and Secretary of State John Kerry used to describe it. Now they want to disengage, and the Ukraine crisis creates a very uncomfortable problem: The U.S. needs Moscow's cooperation as it withdraws the more than 33,000 troops left in Afghanistan because one of its main withdrawal routes runs through Russia.
The Pentagon began developing a supply route from Afghanistan through Central Asia and Russia because of frequent disruptions on the main routes through Pakistan....
Russia has allowed NATO to develop a transit hub at a base in Ulyanovsk to move cargo by air, road and train from Afghanistan through the country to its northern ports. At least a third of the cargo coming out of Afghanistan is expected to move by that route -- if Moscow doesn't shut it down.
If we were going to fight a real war against Russia, of course, we could view our forces in Afghanistan as a kind of pre-positioned task force that could turn its guns around and operate for a while as a second front. That possibility is precluded by Russia's status as a first-rate nuclear power, as well as the challenge of resupply: we'd have to figure out not only how to fight on the Western front, but how to link up a reliable supply to this Eastern front. Either of those problems is huge by itself.
One reason the Russians are moving so confidently is that they have done the math on this. It's possible we might become embroiled in a war because of some basic error on our part. Wars do sometime start by accident. If we do find ourselves there, we've got to tackle those huge logistical problems first.
Clandestine and diplomatic support are the more likely fields of action. Even diplomatic support, however, will be limited by the need to maintain the supply lines to our forces in Afghanistan. It may well be that the Russians will look for any pretext to shut those down, because it would slow our withdrawal. Like the Norse god Tyr, we've stuck our hand in the wolf's mouth, and as long as it remains there it serves as a kind of guarantee of our good behavior.
That's probably just a coincidence.