THE news that federal prosecutors have demanded that the microblogging site Twitter provide the account details of people connected to the WikiLeaks case, including its founder, Julian Assange, isn’t noteworthy because the government’s request was unusual or intrusive. It is noteworthy because it became public.

Even as Web sites, social networking services and telephone companies amass more and more information about their users, the government  in the course of conducting inquiries  has been able to look through much of the information without the knowledge of the people being investigated.

For the Twitter request, the government obtained a secret subpoena from a federal court. Twitter challenged the secrecy, not the subpoena itself, and won the right to inform the people whose records the government was seeking. WikiLeaks says it suspects that other large sites like Google and Facebook have received similar requests and simply went along with the government.

This kind of order is far more common than one may think, and in the case of terrorism and espionage investigations the government can issue them without a court order. The government says more than 50,000 of these requests, known as national security letters, are sent each year, but they come with gag orders that prevent those contacted from revealing what the agency has been seeking or even the existence of the gag orders.