I heard the expression I kid you not used as I was travelling on the train this morning. i have not heard it for quite a time but I suppose its day has come as it takes its place with those other modern pre-affirmaton statements like I swear to you; I’m not going to lie to you. These prefatory insistences pepper modern speech (I’m sure you have noticed). Emphatic and declamatory, I live them as a boorish and boastful preface to mostly banal utterance. They are rhetorical features, I suppose, looking to convince us with stardust, all form, bullying the listener into better attention. What I would prefer is a complex utterance told modestly, rather than this, where we often get dull material given the big intro. It is so much nicer to devine complex material delivered seamlessly, articlately, without shout.