It's easy it is to “speak prophetically” when you know it's what people want to hear.
Every once in a while I find myself preaching for the nod. That’s when we try to hard wire a bit of ego-stroke into a Sunday morning message. We do it a lot, and it’s so easy—insert that small comment, that little aside, or even that main point that we know will appeal to the sensibilities of certain listeners. You know, the left-leaning (or right leaning) political comment. The doctrinal aside that scratches the itch of that person so prone to give up the "Amen" or the vigorous head nod.
Preaching for the nod has less to do with what we see in the biblical text and more to do with what we want people to see in us. And there lies the danger.
The most God-centered, John Piper-esque sermon or community-centered dialogical discussion can be completely me-centered if my intention is to get certain people to tell me, “Good words today, Pastor!” If my intention is to get certain people to see me as sufficiently hip and relevant (or standing against the tide of culture), or progressive (or appropriately conservative), or doctrinally adventurous (or steadfastly orthodox), then I have traded the proclamation of God's Word for the proclamation of myself, regardless of how I dress it up.
And all for that little nod.