Carl Icahn resigns from Blockbuster board

San Francisco Billionaire financier Carl Icahn is stepping down from the board of Blockbuster, effective Thursday, according to a filing with the Securities and Exchange Commission.

In a letter to Blockbuster CEO and chairman James Keyes, Icahn said he was resigning because of Institutional Shareholder Services guidelines regarding the number of directorships a person can hold.

Icahn and his funds currently own about 16.9% of Blockbuster's Class A shares and about 7.7% of its Class B shares.