...that I have a feeling pretty much nobody except maybe Linden will be interested in.
This is what I was thinking this morning as I was putting on my socks: these days when I communicate with people over the Internet I can't necessarily tell what dialect of English they use. If I were hearing their accent I would at least have a clue that, for example, they are from the UK instead of the USA or something like that. But the syntactic and vocabulary differences between the dialects are small enough that most of the time it's not completely obvious which dialect people are using.
BUT, as we all know (hee hee) people and groups use language to distinguish themselves, for social reasons. We don't WANT to be the same as other groups of people. Therefore, in the age of electronic communication, we might expect that the change in morphosyntax/vocabulary of the dialects is going to accelerate, since these kinds of change will be more effective at distinguishing ourselves from each other than phonological change.
Linden, is this EXACTLY the same thing you've already thought of?
(End of me being a crazy sociolinguist. For now.)