The U.S. and EU imposed asset freezes and travel bans on a handful of Russian and Ukrainian officials connected to the Crimean secession. Most of them are mid-level people; a few are Putin aides. They did not impose asset freezes and travel bans on Putin or other big shots, nor did they impose sanctions on Russia itself.
Why not? You can easily imagine that if Putin had been sanctioned, he would not be able to back down or make concessions–because then it would look as if he betrayed Russia for personal financial reasons. But the same logic applies to the mid-level people, who now must redouble the aggressiveness of their stance on Ukraine. And because the sanctions were imposed on a handful of people rather than all of Russia, the Russian government can easily compensate the sanctioned individuals for any losses that they have sustained. Indeed, probably their public standing has increased as the sanctions will make them look important to the Russian public who are probably learning the identities of some of them for the first time.
So the sanctions aren’t even toothless: they reward rather than punish the wrongdoers. They are best seen as a signal, the weakest possible signal, one that indicates that we will accept Crimea if you go no farther. I suspect that it would have been more sensible to send this signal by imposing a weak sanction on all of Russia than to single out these people who will be perceived as heroes who have made sacrifices for the motherland.