Good topic. I don't believe the rules have changed at all. I see reduced following of language protocols (punctuation, spelling, grammar) as the result of a combination of laziness, impatience, increased phone texting/social media activity, increased reliance on spell-checking technology, less formal english education being taught in schools, and most importantly, not caring. Plus in the case of many..."dudes"(and this is where I'll get flamed), it seems intentional as an attempt to appear more "hip". I'm sure I''ll be quickly dismissed as old, but I'm sure I'm not the only one that's mildly disappointed when I see educated adults typing silly things like "Dat ride is fast AF" or completely ignoring punctuation. I acknowledge that we older grammarians tend to less tolerant of change than younger people. If you think about it, at some point, the people that currently don't follow proper those language protocols will probably themselves eventually become less tolerant of similar changes made by the generations that follow them. They'll naturally deny it now. But after we older folks are long gone, I think they will begin to notice it without the burden of having to admit that we were correct (at least about that single topic) It seems inevitable to me.
As far as how long this stuff has been around, I think a very long time. It's just become far more noticeable as technology has become more important in our lives. Between texting and social media, it's difficult not to get barraged with examples of it.
OK, I'm wearing nomex underwear. Flame away.