From a Notice of Proposed Rule-Making posted in the Federal Register by the Department of the Treasury:
The proposed rule would generally require individuals to receive Federal nontax payments by EFT [Electronic Funds Transfer] , effective March 1, 2011, except that there would be a delayed effective date to March 1, 2013, for two categories of individuals, namely: Individuals receiving Federal payments by check on March 1, 2011, and individuals whose claims for Federal benefits are filed before March 1, 2011, and who request check payments when they file.
For Federal benefit recipients, this means that individuals whose claims for Federal benefits are filed on or after March 1, 2011, would receive their benefit payments by direct deposit. Individuals receiving their payments by direct deposit prior to March 1, 2011, would continue to do so. Individuals who do not choose direct deposit of their payments to an account at a financial institution would be enrolled in the Direct Express® Debit MasterCard® card program, a prepaid card program ...