To start, let's notice that labels are often the mothers of ideas. What we call a thing colors our thoughts of it. Are the men held at Guantanamo "prisoners," "captives," or "detainees"? Were the folks fleeing Katrina "refugees"? (Were they "folks"?) Beyond euphemism, we are limited by our ability to categorize. Language is not just the clothing of ideas, it is the mold of them.
The label "mainstream" is pejorative in the context of media. Discussions of the topic of Mainstream Media (MSM) inevitably originate from the backwaters of cultural thought. It may be true that culture is more composed of these than it is of the channel, but critics of the MSM nevertheless voice their discontent from a position of disenfranchisement, almost by definition.
With this in mind, I ask you to consider what we mean by "alternative." This label carries the happy implications of "different," that is to say "better" than the hegemon. The alternative is perforce not the maligned mainstream. But the term also constrains. The "alternative" is forever marginal, always discreditable by its minority.
I mention all of this to give you footing. Our discussion of "alternative media" is flawed from its beginning, flawed by the very terms. But important nonetheless.
