I believe that if you've been studying a language for twelve years, not counting college, then you should have some damn capability to write a cohesive sentence.
The only people who have an excuse are those who are foreigners (some of which actually type better than the enigmatic jargon I've seen people spew out) and those who are elementary school kids, and for the latter category I expect to see at least an attempt at competence or, provided that you're second-grade or lower, you shouldn't be on some place as adult as the Internet AT ALL.
Let me give an example from something I got off of Lamebook.com, a site showing particularly faulty moments on Facebook. Granted, it's an extreme example, but it shows exactly what Grammar Nazis are griefing against.
No. Stop.
This is not acceptable.
Thousands of immigrants entering countries all over the world need to prove their competence in the native language before they can even live there, and you can't articulate something you should've been spoonfed from birth. There is no excuse for this. This is not "slang". This is not "accentuated". This is one of the greatest slaps to the face you can give to your upbringing, marking you as someone who struggles to even get the most basic of instincts down. Furthermore, its use perpetuates the idea that it's acceptable to talk like this on the Internet, and drags down the already deteriorating image of E-communities by turning it into a trademark.
I'm not going any further, but personally, I can't stand it when someone tries to cut corners in something that is supposed to be so completely second-nature as writing.