The point I was trying, and clearly failing to make, greatnan, is that good grammar and spelling ARE taught. Whether certain people learn them or not is an entirely different matter.
I agree that bad spelling or grammar on, for instance, a job application, is indicative of something. Fine. So be it. So it has always been. If grammar and good spelling matter in the job being applied for, you have a fine short-listing criterion right in front of you.
Text speak is not difficult. And it's not a question of getting "down there" with the kids. It's a question of using as few characters as possible because they are limited. Simple really. Same on Twitter. Ergo: textspeak is a useful tool.