Les the Stupid Evil Bastard reminds us all why transparency in government is vital:
[...] you end up with situations like this one where students who engaged in peaceful demonstrations opposing military recruiters at UC Berkeley and UC Santa Cruz ended up in a database that’s supposed to be used for tracking foreign terrorism:The students were angry when they turned up in the database of a Pentagon program called Threat and Local Observation Notice, or TALON, which the government started in 2003 as a way to collect data that could help stop terrorist attacks. Officials have acknowledged that the reports on protests should not have been included.
[...] The reports were filed by the 902nd Military Intelligence Group, the Army’s largest counterespionage unit.
The ACLU managed to find out about the additions via a request under the Freedom of Information Act, but that act doesn’t apply to all government programs and it’s always difficult to question programs you don’t know about because they’ve been kept secret.[...]
What keeping it secret does do is protect the administration from the fallout when the inevitable abuses—intentional or accidental—do occur. “Just trust us” isn’t a good argument as past history has shown many times before.
One common argument for across-the-board secrecy is that transparency helps the terrorists. This argument doesn't hold water. It is better to discourage people from becoming terrorists rather than catch them afterwards. If the anti-terrorism intelligence programmes are effective, and people realise that they are effective, they will be discouraged from becoming terrorism. Secrecy is only worthwhile if the programmes are ineffective and pointless -- in which case we need to know, so we can fix them or replace them.
Terrorists aren't stupid -- or at least, the dangerous ones aren't stupid. They have their own intelligence-gathering operations themselves. They can think ahead and use common sense and act as if they were being spied on, even in the absense of direct proof that they are being watched. Many of them have spent years or decades fighting some of the most secretive military and police organisations in the world: the old Soviet Union's KGB and military, the Israeli Mossad, Saddam Hussein's secret police. There are old terrorists, and naive terrorists, but no old naive terrorists.
Intelligence and security professionals, as opposed to the sort of arm-chair generals who get their ideas about intelligence gathering from half-remembered bad B-grade movies, know that security must be robust to be effective. Murphy's Law holds in the fight against intelligent, dedicated enemies: anything that can go wrong will, and if the effectiveness of your programme depends on secrecy, you can be sure that somebody will find out. Better to assume that not only does your enemy know, but that they know that you know they know, rather than hope that they remain ignorant.