I get frustrated when ALL THREE OF US read/edit an article, and that many mistakes make it into the final product. Two mistakes in the first paragraph? That's ridiculous -- I'm not being facetious -- and it is surprising and disappointing that it happens.

Sometimes, it's just laziness. Chris had a math error in his article yesterday, and that's on me for just reading the article and assuming the math was right, without double checking it before publishing. Lazy.

Other times, there's no real reason, other than we just don't see it. Sounds ridiculous, but it happens. No good reason or excuse for it.