Typos, I can understand. But when I see a person use 'definately' and 'would of', I immediately think, "there's someone that didn't pay a lot of attention in school, if at all he or she went to one" People make mistakes all the time but, the frequency with which some use the above corruptions makes it that much harder for people to correct themselves. It also implies that it is not just a slip-up - rather a habitual mistake made out of ignorance.
I know that 'finite' not 'finate' is the base word of 'definitely'; 'finite' meaning limit or boundary and 'de' being a prefix meaning to set or 'complete'. Definite literally means 'to set or complete the limit or boundary upon'. I never, to my knowledge, spell the word 'definite' as 'definate'.
Now that doesn't sound much like ignorance or lack of education, does it?
So why do I some times have a tendency to spell 'definitely' as 'definately'? I don't know.
If I were to type the word in a sentence or paragraph, then take the time to proof read for spelling, I would likely spot the mistake after the fact. Indeed, where ever 'definately' appears in a vacuum, that is to say by itself, I instantly spot the misspelling. I may be less inclined to notice when 'definately' is used in a sentence.
All ignorance? All deplorable education? I beg to differ.
First, I agree some people truly don't know the proper spelling of some word they're misspelling, but in many cases, not only is it not ignorance, its rather arrogant to presume it is. There actually are many known reasons which explain why a person might habitually misspell certain words though they are in fact not ignorant of the proper spelling.
The brain halves work rather dynamically when combined. The left brain thinks in terms of raw data, the right brain thinks in terms of complete images. Only when combined can complete and meaningful ideas and concepts flow from one's thought process, the spoken or written word.
The words "thank" and "you" mean nothing to the right brain, but the sentiment behind "thank you" does mean something to right brain. Conversely, the sentiment behind "thank you" means nothing to the left brain, while the words "thank" and "you", including the sequence of letters, are meaningful to the left brain.
There are a number of little 'quirks' that can happen between the transition from thought to the written word. Much of the long-term 'archived' information (i.e. that which you have "learned") in the brain is closely tied with an association. Some times, we have no control over that association. It just happens.
I have noticed that in some instances, an association that occurs when I write is phonetical, despite having not learned to read or write by any phonics method, per se. So in a 'stream of thought' or 'consciousness' session of writing, I tend to spell some words phonetically where I have some tight association with the phonetical nature of that word, in spite of knowing the proper spelling. We all, to some degree, learn to read and write phonetically. There is simply no rigid separation between the written and the spoken word as we learn the art of language and communication.
I will not go in depth on two other salient points, except to mention them in brief. One, the Brits have different spelling for various words, like "defence" and "colour". Since the Brits have more rightful claim to the English language than the butchery done to it by their American counterpart, one should be careful not to meet with closed-minded arrogance an encounter with perfectly permissible alternate spellings. Second, English may be the second or third language for many people. How many different languages do you write and speak as fluently as your first?
Perhaps if you read a few more books in the area of psychology or anthropology you wouldn't be such a condescending prick who is neurotic about spelling? Food for thought...
Don't get me wrong, I'm glad we have people who are obsessive about spelling and grammar. They are very valuable, when they're paid or asked to be.