While agreeing that having someone correcting spelling mistakes is a touch like being back in school, there are times when reading posts becomes such an effort because the spelling, punctuation and grammar are so bad. While acknowledging that it isn't always easy, most of these errors could be corrected if the writer just took a little time to read what they have written before they post.
My typing is abysmal, but I try to correct all the typing errors before I press 'submit'. It just seems a common courtesy to me.