The California Superior Court in San Fransisco has proposed that all juror questionnaires include a cover sheet containing the following statement:
You may not do research about any issues involved in the case. You may not blog, Tweet, or use the Internet to obtain or share information.
The new rule (Proposed Rule 7.2, available here) would be effective Jan. 1, 2010. (Note that while the rule states that the new cover sheet is available on the court's web site, it does not appear there. The quote is from coverage of the proposal by Eric Sinrod's "Technologist" blog.)