George Bernard Shaw famously said, "The single best problem with communication is the illusion that it has taken place."
I've worn out countless red pens marking up engineers' memos so they actually say what the engineer thinks it says. It's like there's a crystal clear picture of exactly what the engineer's thinking in an imaginary bubble floating over his head as he writes. Unfortunately, that picture can get lost in translation and there may be an entirely different picture in the imaginary bubble floating over the head of the person reading it. When this happens, you get situations like these (click here).
One helpful rule of communication I learned at home as a kid: "Better to keep silent and be thought a fool than to open your mouth and remove all doubt".