My English can be terrible, even though I'm a native speaker.
I used to be... how to call it?... 'top of the class', when I was in college, and my English can still be good when I think about it (at work, for example). I blame the internet! It makes me use a 'stream of consciousness' way of writing, where I put words in a grammatically incorrect order and... well... write a bit like speaking... :sorry:
Seriously, I do think the internet has changed something about the way English is written (and other languages as well, obviously, but I don't know enough about them to say). Most articles I've seen on the subject blame internet and text messages for 'bad' stuff that happens to the language, but I don't think it's necessarily changing in a bad way. Just... different. One example is the English you use when you're chatting with someone on msn messenger. Totally 'bad' English in the traditional sense, but is it really 'bad'? I don't think so. I think it's just another way of using the language, and if anything making it more flexible. I mean, in the past, only 'educated' people could even read and write at all. Now, not everyone can but lots of people... so the language/use adapts to suit the needs of the people using it, who don't always want something really brainy and formal.
As someone (I've forgotten who it was! Was it Jane Austen?) once said, "Language has been given to us to make our meaning clear, not to hide it". Well, that's debatable! but... you get my drift... the main thing is to get across what you are trying to say.
I've found that typing on forums and emails etc. has made my use of English more flexible... like in my previous sentence I used a lower case letter after an exclamation mark. Technically, that's incorrect, but I do sometimes use it, to try and convey and impression of the sentence moving on quite quickly, rather than totally stopping there.
I'm also finding the use of emoticons is becoming horribly addictive almost to the point of mutating into a kind of 'English kanji'! A sentence begins to look incomplete without some kind of 'mood indicator' attached to it. >< (Case in point. ^_^) It becomes pretty extreme when you start wanting to use them in your handwriting... *sighhh*...... Oh yes, and those little words that go between asterisks... serving a similar function to emoticons, I guess... It seems to me like a way of trying to 'stretch' the English language to make the experience of reading/writing more like talking face to face, where 80% (-ish) of communication is made up of body language.
It might seem a bit childish or philistine or... something, hehe... but I actually find those 'mood indicators' really useful, because it's difficult sometimes in writing to detect what someone is actually thinking or feeling - for example, you can miss out on sarcasm or irony. There have been countless times when the addition of a simple " ^_^ " or " >> " has totally changed the way I've read a phrase...
Ohh... I'm sorry to go on so much... I think I've drifted way off topic.
Please feel free to move this post if it fits better somewhere else!