There was a study done at a nearby University a couple monthes ago that claimed one could mix up the letters of words when typing, but as long as the first letter and last letter of the words were accurate people could still read the sentence. Our brains are so programmed to language we have familiar words patterns memorized. When we see a transposed word, our eyes rearrange the mixed up letters in our heads to reform the proper word.
To ilutsralte tehy snet out an etinre emial wirtten lkie tihs, jsut to see if poeple cluod raed it.
Personally though, I think our typing errors are caused by typo fey. Small impish cyber faeries buzzing around the bandwidth contorting our words. I think they make an 'Off' spray for that, but I enjoy watching the tiny, naked, drunken faeries dance along my keyboard.
Cheers~