I think the use of projection systems in modern churches has been both one of the greatest tools used in worship and one of the most distracting tools used in worship. When done right, the video can really enhance the worship and teaching experience. When done wrong, it distracts from worship and the message. Churches implementing video and projection would be wise to get some training in this area to make sure they're not using it in such a way that defeats the purpose.
This photo I found online today cracks me up a little. Note to churches: If you're considering featuring live video on your big screen, make sure you're meeting in a room that's big enough that it's actually needed. If the actual band looks bigger than the band on screen, it's not needed. Also, if your live video is making your band look shorter and fatter---not good, either!