Take a look at the following article that addresses the idea of interaction during preaching in the worship service: “What You Can’t Say in Church.” I would love to know what other’s think or have experienced with this. At Tidelands worship gatherings I have tried to allow time after many sermons for questions and interaction. I have found that it is often one of the most profound moments in our time together. However, I also know that we are small and that is one of the reasons that we can get away with it. I like the idea presented in the above article though: Preach for a bit, ask a discussion question to be talked about with those seated nearby, and repeat. Of course, coming up with a worthy question would be the key.
Beadle Bailey's Babblings 
Very intriguing sermon format. The fear of the unknown comes with the willing surrender of some control, which will absolutely terrify some pastors, especially those with control issues. It’s great to see you, and many other pastors, are willing to move outside of comfort zones! There’s also a very real fear on the member-side of such an interactive format, as well, because a “questioner” would have to step out in front of everyone with whatever they said. Intimidating, for most folks who aren’t very confident and probably extroverts. Alternatively, small groups are conducive to the touchier (or hot button) discussions, not because we need to keep these topics safely stashed away or hidden, but rather to enable and encourage a deeper level of sharing that isn’t as likely in a sermon Q&A session. A sermon Q&A would normally imply a larger group (unless it’s a very small congregation and/or a tight-knit community where everyone knows everyone).