It is an interesting analysis by George Friedman in Stratfor: Sometimes sanctions do not work at all, and sometimes--at the opposite extreme--they work so well as to prompt war, as when Imperial Japan decided, in 1941, that it would rather declare war upon the US than to meekly accept the sanctions that America had imposed upon it.
The sanctions imposed against Russia are intended, clearly, to be quite impotent.
As Mr. Friedman puts it, in his conclusion:
The U.S. sanctions strategy is therefore not designed to change Russian policies; it is designed to make it look like the United States is trying to change Russian policy. And it is aimed at those in Congress who have made this a major issue and at those parts of the State Department that want to orient U.S. national security policy around the issue of human rights. Both can be told that something is being done -- and both can pretend that something is being done -- when in fact nothing can be done. In a world clamoring for action, prudent leaders sometimes prefer the appearance of doing something to actually doing something. [Bold added]
Here is the link: http://www.stratfor.com/weekly/us-opts-ineffective-sanctions-russia?utm_source=freelist-f&utm_medium=email&utm_campaign=20140429&utm_term=Gweekly&utm_content=readmore