If your Geeknet shares of common stock are held in a brokerage account, your broker is authorized to exchange the shares for you and the number of shares you own after the split should be reflected in your account. You can contact your broker for more information.
If you hold the stock certificates yourself, you will receive a letter from ComputerShare, Geeknet's transfer agent, outlining how you must send your certificates back to ComputerShare to exchange them for new certificates. You should receive the information in the mail in about a week after the reverse stock split takes effect. You can contact ComputerShare and Trust for more information by calling (781) 575-3400.