Teresa Fry Brown makes a startling statement in her presentation of Charles Adams' 9 suggestions to preachers found on page 164 and 165 of her book Weary Throats and New Songs. She says:

One lacks homiletical integrity, authority, creativity, character, calm, and spirituality if one's entire preaching life is stolen.

Brown notes that one should at least credit a source if one uses another's introduction, alliteration, or other device. Stealing sermons hurts you because as you steal, you slowly lose your own creativity to put together strong sermons. In addition, there is a great possibility to lose credibility with the people. I remember hearing a particularly strong sermon from a well-regarded preacher. Later in my seminary study, I was reading a book of sermons and found that sermon word for word. This brought into question all of the sermons that he had preached.

I heard another preacher beginning to whoop, and he simply stole the catch phrases and whooping devices from 2 or 3 preachers and mashed them together. What saved the preacher was that the devices came from preachers from a different theological tradition and thus many in the congregation had not heard them before. Such preaching may get you an "amen," but it seriously calls into question your own integrity as a preacher. God has called you to preach to this people at this time. If God wanted that other preacher that you are copying to preach, then God would have placed them where you stand. Preaching is hard work, but the benefits are enormous, don't short-cut the process for a few ill gotten accolades.