"Typos can make you look foolish, but they aren't really the signs of an intellectual or ethical deficiency. It's the difference between a sentence that expresses an idea badly and a sentence that expresses a bad idea."That's from linguist Geoffrey Nunberg, talking about Bush's use of "nucular" instead of "nuclear." But I think it says something about copy editing, too.
As easy as it is to get caught up in the minutiae of things, the bigger picture is always more important. Readers forgive a typo. They may call in and complain because it looks sloppy, but they'll forgive.
But people don't call when a story is incomprehensible. They get frustrated and move on to the next story. They think about newspapers being written over their heads. They cease caring.