Controlling the news media with one major corporation is a serious concern. The First Amendment in the U.S. Constitution gives us the freedom of speech. If the news media was controlled by one major corporation, our First Amendment rights would be impeded. It's critical to get all sides of a story, and small parties of news media that work independently of one another would hopefully report news that is not misguided or manipulated.
I don't think that there is much to say that hasn't already been said above/below (I don't remember where this will appear). Nothing good can come from viewpoints being silenced by one person who does not agree with that view. Also, monopolies are bad because it limits people's choice in what they see.
The media should be controlled by a number of small parties so that different views and ideas are presented to the people and something which would not be possible if it was controlled outright by one entity. The media is for freedom of speech and establishing a monopoly over it's use goes against it's primary function.
I believe that news media should be controlled by multiple, small parties that contribute to the accurate dissemination of news. When one company controls the majority of a reporting agency it is easy to let a variety of factors, including political or financial gain to play a role in how the news is being reported. If our society really valued communicating the truth in every situation it would not make a difference, but because too often individuals and corporations are concerned with their own interest, news can be skewed when a monopoly is in place, often resulting in either over-dramatized reporting leaning towards a conservative or liberal view. In regards to reporting, the more parties involved give a more likely chance that a view closer to the actual truth will be reported due to the accountability through all parties involved.
No market should be controlled by one commercial corporation. This is a definiton of a monopoly and leads to market failure, with serious detrimental consequences for the population. In the media it stops the dissemination of different opinions which can be very dangerous in a variety of circumstances - only one political view may be aired, there is lack of challenge to the status quo, and it shakes the foundations of democracy. A free press and media requires multiple owners of the media.