It's not a threat to shorts at all. Go to the SEC;s website and get the real story. This is he beginning of what the SEC says and from their website: "Regulation SHO became effective on September 7, 2004. (Securities Exchange Act Release No. 50103 (July 28, 2004), 69 FR 48008 (August 6, 2004) (�Adopting Release�)). The commencement date to comply with the provisions of Regulation SHO is January 3, 2005.