1) Of course. After all, they are a business and have their own bottom line. Take the Snowden revelations for example. Many were published but some, at the request of unnamed government officials, were not. Look at James Risen of the
New York Times. He's being dragged through the mud for not giving up his sources. Or look at the Bilderberg meeting this year: ABC, CBS, CNN, FOX, MSNBC & NBC had 0 coverage. So media co-option by the government is visible if one looks, but the extent, the true extent, is unknown.
2) Yellow journalism helped get us into World War 1.
3) While the media doesn't have unfettered access to government held information, they do, however, have unfettered access to the Internet, social media & e-mail. Personal story: when I watched DNI James Clapper say that there are sleeper cells in the U.S., I e-mailed the NYTimes, the Washington Post, the LaTimes & the WSJ with the video (which is curiously missing from Youtube now). None of them ran the story. It was from this hearing:
Intel Chiefs Testify at Senate FISA Oversight Hearing | C-SPAN