Strictly regarding the spelling, grammar, and language issues involved, and stepping slowly and carefully around the MPG debate (which, as Angus points out, is actually beside the point entirely), I believe we are in a period of rapid evolution -- both of society and of the very fabric of language.
I agree that the ability to spell and compose sentences is fading away. This is not a new phenomenon, though. One only has to read the correspondences of people, say, 150 years ago, to see a basic difference. The letters of Civil War soldiers, for instance -- and not of the so-called "educated men" at the front, but just the average men from farms and cities across the country -- were astonishingly eloquent by modern standards. This difference didn't just occur with the advent of computers; it's been an ongoing process of change in our society, and not an erosion of thought or culture.
Language is an exceptionally dynamic thing, and it will change as the times and cultures of it's users do. Words come and go as required by people -- as do the rules of grammar. Many Victorian-era sentences would be considered run ons and poorly formed if written today. And I, too, find the misuse of words like "your, you're, and yore" to be difficult to read.
But let's be honest for a moment: having three words that are spelled similarly and pronounced the same, yet which have entirely different meanings is ridiculous! This is not intuitive by any means and it's hardly necessary, as constructed languages like Esperanto prove out. We tend to consider a person who cannot use these words correctly in written communication as being at least somewhat ignorant -- and I suppose they are as far as that goes.
But today's English will not be tomorrow's, and technological influences like spellcheck programs will have a place in that evolution -- just as the printing press had an eventual influence in codifying the English language (acting mostly as a spur by making the written word more and more common in everyday life, and thus, starkly illuminating a very real need to make the spelling and construction of it less idiosyncratic and easier to read).
Angus' friend was convinced his car's computer was right, and more-or-less refused to hear any counter-arguments. Has he given up on thinking, and turned over his decisions to a machine? Well, possibly, but throughout all of human history, at all technological and sociological levels of progress and decay, there have always been stubborn men. You could just as easily make the argument that technology is the new religion for many people, and that some of them are dogged, even pig-headed, in their blind faith in it. There's always been something that some people have had perfect trust in for less-than-logical reasons. Very often they're right (if for no other reason than statistical chance), and this only reinforces their opinion...or the object of their faith fails them somehow, but this failure is put down to some prejustified reason or other, which, again, only reinforces their view. It isn't until there has been a shift in society as a whole that you see the old faith fade as a new one comes along to replace it, because there will always be a new one to replace it.
I don't know this guy, of course, so I can't speak to his personality, but I've met people who act this way -- some of them quite smart and/or highly educated -- and it mostly comes down to temperament and worldview, I think. And I'd hazard to say that if you had a time machine, you'd find lots of people, both in the past and the future, who do the same thing. Computers are tools, and you either trust in your tools and your ability to utilize them, or you don't. And you either have an open mind about them or you don't. This comes from experience and personality, I believe, and not from laziness.
Going back to the language issue for a moment; why do you suppose we see CEO's and important world leaders today, in addition to ordinary folks, who can't spell or construct sentences worth a damn? You can say it's the schools or the influence of technology or the alignment of the stars, but the plain fact is nobody cares. It's not very important anymore to most people if you can string two words together -- that's seen mostly as a specialized skill or talent, much like plumbing or electrical work, which can be hired out or delegated if deemed absolutely necessary, or ignored if not. And few people have a problem with this anymore, because if they did, it wouldn't be tolerated. In days of yore, people who filled their letters with misspellings and bad sentence construction would have never risen in any organization. But in this day and age, why bother sweating over details like proper English spellings or transposed words when you have spellcheck and a secretary or intern to take care of those details; or even if they don't take care of them, few people will even mind or notice?
What's important to us today is different than what was important yesterday, and different still from what was important the day before. It stands to reason, then, that tomorrow's values will be equally as alien. We're not likely to find the change a comfortable one; but someone, someday, will look back at our time now with surprise, wonder, and maybe some envy for our abilities. And like our current lament for the fading of certain skills in our society (read that, changing times), the admiration of us by future generations will likely tell more about what they value -- or even romanticize -- than it will about what we do now.
Yeesh! This is disgustingly long! My apologies to anyone who made it this far!
-David
??? 
;D ;D ;D That's irony for you.
