Where's the dividing line?

I picked up the Des Moines Register yesterday and was amazed at yet another government secret unrevealed. Looking farther into the issue online, I found the article "Europeans seek more info on secret jails" which discussed how CIA secret prisons exist.

Bush said in a White House speech Wednesday that a small number of
high-value detainees - including the mastermind of the Sept. 11 attacks,
Khalid Sheik Mohammed - had been kept in CIA custody in order to be "held
secretly, questioned by experts and, when appropriate, prosecuted for
terrorist acts."

The government's gatekeeping process is at times scary. When you really contemplate the idea of "secrets" being held from us citizen's, it really makes you want to question what else is being withheld from us. Knowledge is power, so is this just a building block to the government's hegemonic stystem? Is there a fine line between holding information back that 'protects us' and knowledge that should be told straight up?