[National security letters], the reach of which was expanded under the Patriot Act in 2001, let the FBI get business records from telephone, banking, and Internet companies with just a declaration that the information is relevant to a counterterrorism investigation. The FBI can get such information with a subpoena or another method with some judicial oversight. Can the government make demands for data entirely in secret? That was the question yesterday before a federal appeals court in San Francisco, where government lawyers argued that National Security Letters - FBI requests for information that are so secret they can't be publicly acknowledged by the recipients - were essential to counterterrorism investigations. One of the judges seemed to question why there was no end-date on the gag orders, and why the burden was on the recipients of NSLs to challenge them. It leaves it to the poor person who is subject to those requirements to just constantly petition the government to get rid of it," said the judge, N. Randy Smith. The FBI sends out thousands of NSLs each year - 21,000 in fiscal year 2012. Google, Yahoo, Facebook and Microsoft filed a brief in support of the NSL challenge, arguing that they want to "publish more detailed aggregate statistics about the volume, scope and type of NSLs that the government uses to demand information about their users." Twitter also announced this week that it was suing the U.S. government over restrictions on how it can talk about surveillance orders. Tech companies can currently make public information about the number of NSLs or Foreign Intelligence Surveillance Court orders they receive in broad ranges, but Twitter wants to be more specific.