Here's Susan Herring:
Various attempts have been made by linguists to classify CMD [computer-mediated discourse], starting in the 1980s and early 1990s. Accustomed to dealing with two basic modalities of language – speech and writing – these linguists first asked: Is it a type of writing, because it is produced by typing on a keyboard and read as text on a computer screen? Is it “written speech” (Maynor 1994), because it exhibits features of orality, including rapid message exchange, informality, and representations of prosody? Or is it a third type, intermediate between speech and writing, or in any event characterized by unique production and reception constraints (Ferrara, Brunner & Whittemore 1991; Murray 1990)?
Herring, S. (2007). A faceted classification scheme for computer-mediated discourse. Language@Internet, 4. http://www.languageatinternet.de/articles/2007/761/Faceted_Classification_Scheme_for_CMD.pdf