Proofreading is harder than it looks.  For one thing, anyone who writes a piece ends up too close to it to see all of  the glitches.  For another thing, even the most diligent proofreader can miss something, when you have to check grammar, composition, spelling, sense, sound, and facts.  Written materials are imperfect and always have been.  When I took Old and New Testament courses  in graduate school, the professors made many references to scribal error in the composition and copying of ancient manuscripts. Modern technology has not only not eliminated scribal error but added new kinds:  spellcheck error, cut-and-paste error, find-and-replace error, we-don’t-do-typesetting-anymore-and-can’t-afford-proofreaders-so-it’s-up-to-the-writer-error….

Readers are offended by egregious errors in reputably published books, periodicals and other written material.  Fortunately there’s a balance point just this side of impossibly perfect.  I’m one of several volunteers who proofread for a classical music  performance organization. Our newly minted publicity brochure was found to have a one-letter error in the title of a work to be performed next season – “B Minor”  instead of  “D Minor.” Our fearless leader, Jan (who has a PhD in English from Rice University and is a professor of composition and grammar and superb writer) had a wonderfully sensible reaction.   “I’ll check the web to make sure it’s correct there,” she e-mailed.  “I’m sorry about the error, but it’s not devastating–will give a couple of sharp-eyed people joy to discover it, and most will never notice.”