Mikey posts here about the dangers of conversation brought out in Phillip Jensen's The Archer and the Arrow: Ouch indeed!
I think this is really important. Preaching must always be 'heraldic' - it means to 'herald' or proclaim the message that God declares. So it carries his authority because by leaning on the authority of the Apostles and Prophets who authored the Scriptures, true preaching give a message that comes as the very word of God.
I think it's fair to say that the rise of the 'conversational' approach seen in the modern 'bible talk' can undermine the very act of preaching. I think a lot of this may have unwittingly grown on us undetected from within our culture of anti-authoritarianism.
More of my thoughts on preaching here where I've summarised some of John Stott's stuff.