I know someone who, when she writes to friends, writes exactly the way she talks with them...including tossing in words like, "Hey" and "y'know" and "like" ...so even though she CAN write properly (in her professional life she writes very well) she DOESN'T when she is writing to friends. If someone who didn't know her professionally saw some of the letters she has written to friends, they would assume that she didn't know how to use proper grammar, sentence structure etc.
