The media can influence society through its depiction of events in order to galvanize public opinion. Throughout United States History, there have been moments where the media has played a vital role in shaping and molding public opinion. Edward R. Murrow's exposure of Senator Joesphy McCarthy's motives helped to bring to light his self serving agenda, and end his hunt for Communists through his House Unamerican Activities Committee (HUAC). The media's portrayal of the war in Vietnam, bringing its horror into the living rooms of millions of America on a nightly basis played a very large role in the increasing public discontent regarding the role. The actions of Woodward and Bernstein in the Washington Post helped to influence society against the actions of Richard Nixon. At the same time, the media's use have influenced the public to, at times, see superficiality as accepted truth. Political campaigns' desire to reduce candidates to a quick sound byte is reinforced by the media, as well as individuals in the position of political power finding ways to manipulate the media for its own benefit through selectively telling the truth or through disseminating false information.
You can look no further than the various networks and the news they release. Although the media news is supposed to be relatively neutral and unbiased, anyone who has watched various news programming on the Fox Network over the years can attest to their conservative leanings. Fox was highly supportive of President Bush and continues to be the top basher of the Obama administration. Fox, of course, is not alone. Most newspapers advocate certain political candidates, both local and national, and their opinion pages in particular showcase their leanings. In my area of Central Florida, for example, the Orlando Sentinel is still a bastion of conservative thought, and their opinion pages, as well as some of their feature stories, reflect this. Conversely, the Daytona Beach News Journal is far more liberal minded, having supported every Democratic Presidential candidate since John F. Kennedy (as I recall). Networks and newspapers are not always as blatantly one-sided as many other sources, but they leave their imprint on their finished product nonetheless.
It is hard/impossible to know if the media has actually caused people in society to change their minds on an issue. But here is one where it seems likely that media have had a large influence.
Here in the US, we have, in the last ten years or so, started to have a lot of new laws limiting the areas in which sex offenders (released from prison) can live. They have spread to the extent that released sex offenders are effectively banned from many communities.
You can argue that these laws are caused by the media's reporting on crimes against children. Since kidnappings of kids for sexual purposes (or sexual assaults in general) get so much play in the media they seem pervasive and make people afraid. Once they become afraid, they support these laws. Furthermore, when they hear of other communities passing those laws, they want similar ones in their own communities.