For anyone interested in the history of the people behind the coin instead of market speculation...

The Oglala Lakota people live on the Pine Ridge reservation and have a long history of political activism and resistance.
The American Indian Movement was active there and involved in the Wounded Knee incident - an armed siege against the FBI in the 70's, which could explain the Fed's quick interest in the coin.
You can watch a documentary on it at youtube called "Incident at Oglala".
There was also a Val Kilmer movie called "Thunderheart" based on a fictionalised version of the events.