One of my favorite troublemakers is Frank Viola. When George Barna "entered" house church world (through his writings, at least), one of my comments was that he had not actually connected with any of the people in house church world. In other words, Barna was saying all the things house church people say, but not providing any solutions or awareness of the house church movement. And, I found Revolution to be a relatively unhelpful book for that reason (and several other theological reasons I have stated elsewhere).

In the follow-up book, Barna seems to have jumped whole hog into the house church world with none other than Frank Viola. Together they published Pagan Christianity which riled a lot of people up (me included) and not just because of the not-so-subtle title. For what it is worth, I think New Testament scholar Ben Witherington did a great job in his series on the book (starting here) and Frank was gracious in his response.