ABSOLUTELY; teaching spelling is VERY important. I taught English in China for several years, about 13 years ago, and then returned to my original profession of English editing and curriculum development. I have been working for a Chinese publishing company as an editor and textbook author for ten years now.
It has been interesting to see the attitude of my Chinese students from years ago and now the attitude of my Chinese colleagues to the importance of spelling and other basic errors. "Yes, it is very important to spell/punctuate correctly"--but in practice, 差不多就好了, i.e. "Close enough is good enough". I can't count the number of times that I've tried to explain to colleagues that spelling, punctuation and grammar are such a basic part of language that simple mistakes in those areas will pretty much destroy any impression that they have "good English" or whatever other language they're trying to claim to be fluent in.
It's one thing to be making basic mistakes while learning English; that's just part of the language-learning process. However, when you're in the professional world and using English as a tool, then errors in spelling, the most basic aspect of a language, can, well, make you look very, very bad. In the professional world of business or of academia, basic spelling errors can give the impression that the writer is not very professional in his actual area of expertise, since he can't manage even a simple matter like avoiding spelling mistakes.