Maintaining interest. Interaction does not guarantee interest. Verbose, divergent responses do not assist audience interest at all. So interactive preaching will always be a risk. But effective interaction and involvement of the audience can produce far greater audience interest than straight monologue preaching.
Ownership. We know that people are far more likely to be involved in and committed to projects and decisions when they take ownership. Interactive preaching offers the possibility of sermon ownership. It can be the audience's sermon, not just the preacher's sermon. Ownership of the sermon increases the chances of behavioral change in response to the preaching.
Illustration and application. Any preacher, no matter how well read, has limited life experience and therefore a limited supply of illustration and application. That supply can be greatly enhanced by using the life experience of the audience. For example, most preachers spend more time with Christians than non-Christians. However many listeners spend their working life and much of their social life with lost people. What a resource this provides for preaching. Interactive preaching allows the use of this resource.
Variety. Regular preaching to the same audience can become mundane as the preacher runs out of interesting illustrations and new perspectives. Interaction provides variety.
Having considered the reasons to introduce interaction in your preaching, let's recognize some of the barriers to effective interactive preaching and how they may be overcome. Please understand that interaction is not without its disadvantages. It takes a brave preacher to give up absolute control over the sermon and open it up to the audience.
Lack of authority. The authority of preaching is traced back to the authority of the Word and the Spirit. As the sermon is preached, the main preaching idea is announced with authority because it is the Word of God and the Spirit empowers the Word to touch the hearts of the listeners and bring change. Our authority is greatest when the Word is allowed to speak and when the Spirit moves through the God-honoring life of the preacher. Interaction may block both these channels of authority with the clouded understanding and unprepared lives of the listeners. The preaching may therefore lose its authority. This is certainly a danger that must be avoided. However it must also be recognized that sometimes the listeners may have greater authority than the preacher, when they speak from deep experience and trust in God. I have seen God move in great authority through obedient listeners who are prepared to honestly talk about their lives. But generally, authority is preserved by designing the interaction to supplement the main theme, and to expand, illustrate and apply the main ideas discerned by the preacher under the authority of Scripture.