One characteristic of the Japanese language is that it can express social identities by the mode of speech adopted: it can sound polite, aggressive, old, young, manly, girly, etc. just by changing how you call yourself. The content of the utterance itself does not have to change. Of course, this can be seen in many languages, even English. What is unique to Japanese, however, is that the degree of this embeddedness of the social identity in the utterance is very high. Many other language can express this through the body-language or non-verbal operation of the body. Japanese, on the other hand, make use of the verbal very strongly.
On the web, this may cause an interesting phenomena which cannot be observed in the English sphere: strong schismogenesis. Take the culture of 2ch, for example: language used there strongly differs from the 'normal' Japanese language, yet comprehensible. This creates a certain type of discourse that is differentiated from the 'real' world. Moreover, people may accuse each other for adopting a certain mode of talking.
Again, this is not to argue that other languages do not have this characteristic. In Britain, for example, the vocabulary used by the higher class and the lower class is very different. Youths may use a certain form of abbreviation (e.g. "r u ok?"). However the Japanese language can encompass something much more than that. It can express the class, gender, feelings, level of politeness, etc just by changing the verbal expression, which may result in debasement of the value of non-verbal expression.