The U.S. Patent and Trademark Office has filed a "Notice of Abandonment" to inform Sony its The Last Guardian trademark has passed its 3 year deadline.
Under US law, Sony had until January 2013 to "prove use in commerce" for the long-in-development Team Ico title, but since it's still not released since the trademark filing in 2009 its status has officialy switched to 'abandoned'.
But PS3 owners probably shouldn't be concerned; as Kotaku points out US law makes it difficult to "park" on a trademark without proof it's intended to be used, and Sony can request an appeal or file a new registration.
Last Guardian designer designer Fumito Ueda announced his surprising departure from Sony late last year, but committed to finishing his duties on a contractual basis.
Back in February, Worldwide studios boss Shuhei Yoshida confirmed Sony's drafted in a number of Western Sony developers to support SCE Japan Studio's Team Ico on the highly-anticipated title.