SimChurch: Being the Church in the Virtual World asks very good questions but (in my mind) comes to the wrong conclusions.
To summarize Estes, he claims that virtual worlds (such as Second Life or World of Warcraft) are real places where people increasingly live, work, play, and interact. As such, they are also a space where the Church needs to go to evangelize and disciple. This includes planting virtual churches. As opposed to more broadcast methods of ministry (think televangelism or podcasts), Estes claims that the richness of interaction afforded by current technology lets us do (at least nearly) everything a local church needs to do. In some cases, he claims we need to develop new ways of "doing church" that are better suited to this new medium that may even be better than real-world churches. In the process, he touches on topics such as presence and community, the mediated nature of technological connections (e.g., via avatars), "lifeblogging," online worship, church authority, online sin & accountability, and virtual communion and baptism. He is honest in pointing out the problems, such as with communion and baptism, but remains very optimistic about doing virtual church and how it can be a significant part of the Church Universal.