Why does gov't law enforcement have to be secret?

In this Wired article, we are reminded that one of the neat things the FBI has been involved in has been the abuse of National Security Letters:

A national security letter is an informal administrative letter the FBI can use to secretly demand customer records from ISPs, financial institutions, libraries, insurance companies, travel agencies, stockbrokers, car dealerships and others. NSLs have been used since the 1980s, but the Patriot Act, passed after the September 11, 2001 terrorist attacks, and a subsequent revision in 2003 expanded the kinds of records that could be obtained with an NSL.

There are a couple of really fun parts to this story. First, it took six years for the courts to decide to lift part of the "no telling anyone" ban, EVEN THOUGH the FBI dropped it's demand for some of the information.

Seriously, go read the article and find out what kind of crap our government is allowed to pull on us mere citizens.