Why do so-called ‘educated’ people say, “The social media is a big factor….”?

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The reason I used the adjective 'educated' is because I saw a comment on a website for book editors written by a book editor that used the construction, "The social media is a big factor in the spread of e-books." Now, I could see making an argument that you could put all the social media in one lump and consider 'it' one big thing, but social media include e-mail, blogs, facebook, myspace, just about everything on the internet, so to me it doesn't make sense to lump them together. The word "media" is plural.