This post at Yarn Harlot was very true, although I hadn't thought about it in those terms. She talks about errors in knitting patterns, which is something that I only recently even thought about occurring. For some reason, I always assumed that knitting patterns (and crochet patterns) were checked to within an inch of their lives, and that there's no way that a mistake would be printed in a magazine or book, and that if there was a mistake, it would be a very, very rare occurrence, and the magazine or book publisher would be filled with chagrin and remorse for letting it happen.
I figured out awhile ago that that was naive, and that any time I'm contemplating knitting something from a pattern, a part of that process should be to check online and see if there are any corrections published to that pattern, before I start.
Not to pick on any one particular magazine, but looking at the
Vogue Knitting corrections page, it looks like they seldom publish an issue in which any of the patterns are without errors, and some issues apparently contain nothing but errors.