One of my heroes in this world is William Labov, who once said something to the effect that the secret of life is to get the world to pay you to do something you want to do anyway; he, of course, was famous for mapping American dialects carefully. In fact, he was quite good at it, and went out across the US (or had his minions do this) to record people speaking and document where, for example, one would say "soda" instead of "pop", or how one's vowels actually sounded.
This geographical mapping has shifted and become much less distinct, due to the fact that everyone is watching the same television, and interacting heavily in an online world that has YouTube, Facebook, and digital television shows. The new dialects in writing are caused by the technology people use to produce what they write. So, for example, if people make non-words (like definately) you know that they not only had no spell-check interference, but also no auto-correct function, that on modern programs, would simply change this to the proper spelling.
What I'm saying is that if I can become better at spotting the differences in the ways computers alter people's writing, I'll be like Labov. There was a famous story once, of a guy who claimed to be able to place what block of New York City a person lived in, based on that person's accent, after hearing that person speak for a while. This claim was actually backed up, or it was said that the man was reasonably accurate; I'm not sure it was Labov. But the people in single little blocks of New York City are no longer spending as much time talking to each other; instead, they are online with old friends, and their language is not as distinct as it used to be. Their writing, however, gives us infinite clues, which, so far, most people have been unable to read. it's the modern version of dialects.