As for the main disadvantage: the media need revenue. Revenue tends to be tied to reporting more dramatic events. In absence of truly dramatic events, the media develop tendency to "dramatize" (especially when it gets to political events). As a result we are observing what is usually called polarization. Media to the left and right of the center will tend to amplify certain aspects of reality. Viewers will then tend to focus on sources matching their own (political) affinities. Media source thus develop their own virtually separate audiences. A cycle of polarization emerges.
This is obviously bad for democracy which is based on the principle of educated decision making by every citizen. Citizenship has been more and more polarized and their decision making on issues delineated by political boundaries. Clustering is a problem. For instance, someone who cares about protecting the environment faces a decision whether to join a cluster of political views that include environmental protections (but also other views lumped together with environmentalism by the process of polarization), or completely stay away from that topic. That is bad for democracy.
The moment you see a person pronounced guilty vs. not-guilty by a vote that almost exactly splits down by the political affiliation of the voters, we know we are having a problem.
