Spell-checkers have given all of us a crutch when it comes to writing; we let them fill the gaps in our lacking spelling capabilities.
We've stopped memorizing the phone numbers of friends and family and have given that responsibility over to the contact lists in our cell phones.
I've found myself using yet a new crutch, the iPhone typing auto-complete/correct functionality. In order to compensate for users hitting the wrong keys on the tactile-less soft-keyboard on the iPhone, Apple dropped in some software that determines what I intended to type, even when I screw up a few letters. For example "lrtters" automatically gets converted to "letters" so I don't have to a) either type more slowly to get it right the first time, or b) have to go back and correct the mistake myself.
I can type very fast on the iPhone thanks to this auto-complete/correct feature. I've gotten intentionally lazy at hitting the correct keys because the iPhone is surprisingly good at figuring out what I intended to type anyway. Why should I bother trying to hit the right keys!?
Next step will be building in some contextual and grammatical nuances to the system can auto-correct even the most horribly butchered words.