On January 24th, the US Federal Courts Judicial Comittee on Court Administration and Case Management for the US District Courts issued instructions to be provided to jurors regarding the use of cell phones and computers during their service.
A Network World article posted on February 2, 2010 titled - Courts move to ban juror use of Blackberry, iPhone, Twitter and Facebook provides a summary of this action.
The court instructions can be downloaded in PDF at: http://www.uscourts.gov/newsroom/2010/DIR10-018.pdf