It's a very prevalent thing online, bad grammar/spelling. Back when I first joined the e-community over a decade ago, I was already a big fan of spelling and grammar (I was always shoved in advanced English courses in grade school, and by 13 I was already an avid reader so I knew more or less what was "proper English"). I was constantly correcting people's spelling (not so much on grammar, though) and was always shouted down for it. "We're not in school."

Well, my mother always told me you don't look any dumber than when you speak improper English, so that's pretty much how I look at native English speakers who type badly. I corrected a lot of people in chat programs, and still roll my eyes at those whose ability to spell rates with a six year old's. In chat forums such as this, I type as I would an essay or paper I'd be submitting to a professor. In messengers, I'm not as anal, but it's only barely noticable (I don't capitalize every letter I'm supposed to, but punctuation, spelling, and most other rules of proper writing I still follow). I decided not to let it bother me seeing how bad other people write online; for one thing, some people I've met don't have English as their first language, so slippages often do occur and you can't really fault them for it. I don't keep track of how much "short speak" I use on here, but I assimilated a lot of the acronyms from my old gaming days and used them quite frequently (one I've had to suppress more than most on here being the "what the--" one). I try to avoid using those acronyms as much as possible, though, but when it comes to something funny, "lol" just seems appropriate.
As for straight-up l337, I hate it. Frankly, I think whoever came up with the concept of making it a verifiable e-language needs to die.