This excerpt taken from the SIRI DEF 14A filed Apr 30, 2009.
Shareholder Rights Plan
On April 28, 2009, our board of directors adopted a rights plan to protect against limitations on our ability to use our net operating loss carryforwards and certain other tax benefits to reduce potential future federal income tax obligations. The rights plan is intended to act as a deterrent to any person or group acquiring 4.9% or more of our outstanding common stock (assuming for purposes of this calculation that all of our outstanding convertible preferred stock is converted into common stock) without the approval of our board of directors. We plan to submit the rights plan to a stockholder vote by June 30, 2010, and if stockholders do not approve the rights plan by this date it will terminate. The rights plan will expire on the earlier of (i) August 1, 2011 and (ii) June 30, 2010 if our stockholders have not approved the rights plan as noted above. Additional information regarding the rights plan is available in the Current Report on Form 8-K dated April 29, 2009 filed with the Securities and Exchange Commission.