Putin know that West won't impose any economy sanctions because they will hurt all parts. Putin perfectly aware that Obama and Merkel just corporate puppets, their mission is to protect markets with profit and so they won't really do anything that will hurt global economy. In this way whe worse that could happen to Russia has already happened. Now Russians can go ahead.
When someone ask me how far Putin will go in occupying Ukraine, I tell as far as we'll allow him to go. So far they met no resistance. Crimea was easy trophy because Ukrainians do not see Crimea as historic territories of Ukraine, they wouldn't die for Crimea. 22.000 Ukrainian military men in Crimea are mostly etnic Russians who live there with families. They mingle with Russians from Putins army. Many of them will stay in Crimea, some giving up now. Kiev understand that we can not count on them, that's why our president do not give command for army to retreat. I believe our government loosing them intentionally, kind of getting rid of this army.
http://www.angelfire.com/extreme4/kiddofspeed/maydan/updatemarch22.html
"kiddofspeed" veracity has been questioned in the past, but in this instance the thinking of the average non-Russian Ukrainian (and the gov't) is probably not too far off.
To say that the border was closed to keep Ukrainian citizens out of the Ukraine is not accurate. The Ukraine is closing it’s border with Russia. Russia wanted an island then give them an island.