"The problem with the dash-as you may have noticed!-is that it discourages truly efficient writing. It also-and this might be its worst sin-disrupts the flow of a sentence. Don't you find it annoying-and you can tell me if you do, I won't be hurt-when a writer inserts a thought into the midst of another one that's not yet complete?"
My problem has always been (and it is shared by others) that when one is thinking (or even just musing), we surround our ideas with parenthetical thoughts (which, to my mind, bracket every moment of waking life) and they become, in their own way (or "in the way", as it were) intrusive. And yet colorful.