Brian Patten's poem 'Gust Becos I Cud Not Spel' is about a child who becomes a dictator, rounds up everyone who teased him about his spelling and has them shot. (It's more amusing than it sounds.)
While bad spelling won't get you shot, it will reflect badly on your business. The very least it will do is make you look unprofessional and annoy customers; but it could sabotage deals.