I don't think they have the power to exercise total control or prevent (much of) the truth from eventually coming out, in particular now that alternative sources have become more widespread. Again it's a balancing act -- mixing some of these things into the mainstream sources which are meant to be trusted helps to lend them credibility, and there seems to have been no serious repercussions to any programs or the players involved from the Snowden or Abu Ghraib leaks.

https://en.wikipedia.org/wiki/Limited_hangout