Nowadays, people write e-mails that can be misinterpret for other people. I have done this, but because when you read an e-mail you can not grasp the ironies or jokes.
In my opinion netiquette is a good form for comicate to people that aren´t in your circle of friends, like teachers, work staff...All depends of who are you talking to.
With friends I use abbreviations, emoticons and a colloquial way of speaking. I think that in these cases I don´t need the netiquette.
But with the other people I use a formal way of speaking. Without spelling mistakes and a good grammar.
I never have written anything I woludn´t say out loud, It´s something that I have very clear.