Wikipedia community votes 75% in favor of CC BY-SA:
"The Wikimedia Foundation (WMF) has proposed that the copyright licensing terms on the wikis operated by the WMF - including Wikipedia - be changed to include the Creative Commons Attribution-ShareAlike (CC-BY-SA) license in addition to the current GNU Free Documentation License (GFDL). This will affect all text and rich media (images, sound, video, etc.) currently licensed under "GFDL 1.2 or later versions".
via CC blog