This is an interesting take--could you say more about it? Media is so much more fragmented now than it was in, say, the 1950s, when you had three channels from which to choose your news, one or two major newspapers in most cities... I don't think media monopolies are actually *new*.
In 1953 73% of the newspapers available in the United States were independently owned. Today, 6 corporations own 90% of the news media industry.
That ignores the *myriad* other news sources. Newspapers aren't where people generally get news anymore. We can no longer agree on facts because our news sources are so widely divergent. There were things to dislike about the media landscape then, but "less centralized then" isn't quite accurate.
I've read Bagdikian too, and he was right at the time--but he didn't predict what the Internet would do to media consumption.