I can see this thread turning into a mess.. But I'll throw in my two cents anyway.
I think it's just a matter of how you were raised interacting with keyboard. For example, I grew up on the computer, I quickly learned how to type accurately and efficiently. In fourth grade, actually, I had a typing speed of 60 words per minute while my classmates were still around 15. So, for me, at least, I don't typ lik dis bcus I know I'm much faster typing eloquently. But if you've grown up typng lik dis den u can typ mch fstr lik dat so its undrstndbl 2 tlk lik dis.
I just think it reflects your own personality. I'd like to consider myself an okay speaker, and I'd like my typing to reflect myself. As others have posted, if I want to be taken seriously, I want to sound as formal as I possibly can, to clearly voice my opinion. But I'd like to be taken seriously most all of the time, so.. shabam. I am, however, subject to saying 'Lol' or 'Rofl', those kinds of things. But it's actually slunk into my speech, really. I say "Lol" all the time, or "Jk," "Brb," etc.
I don't think it's going to change, really, just get worse as it becomes more and more widely accepted. I saw a billboard once advertising a bank that used txt-speak on the advert. I was appalled, but I thought, "Y'know, that'll prolly reach more people because they're 'down with the times' or something." And it's sad, but it's true.
But as far as grammar goes, it's understandable if they're foreign or something. But otherwise, people need to slow down and think about what they're about to say, whether if they said it aloud in a conversation if people would be able to follow it.
[/2cents]