According to marketing expert Seth Godin, they do!

Glad to see an influential marketing expert highlighting the critical importance of language correction and correct spelling. It is as important for your original materials as it is for your translated materials. You know that IBM, Sony, or any other leading global company wouldn't allow any misspellings in their message. So if you want to portray as professional an image as theirs, you shouldn't allow them in yours either!

More thoughts about the subject on this recent post.