When thinking about who or what constitutes a "Church" it is really impossible not to look at Matthew 18:20. In this very well-known verse, Jesus says that wherever there are two or three gathered together in His name, He will be in their midst. The words of this verse have long been used by both those inside and outside the traditional denominations to claim the authority of Jesus over what they call "Church". The argument is that if we have a group of people, no matter what size, who come together, and talk about Jesus, or in some way claim affiliation with Jesus then that IS Church".
So, is this really what Jesus is saying to His disciples here, is he really placing a rubber stamp in the hands of His followers that allows them to declare any gathering loosely related to Jesus as the "Church"? Somehow, I cannot see this really being the intent of Jesus; in fact, I think it may be quite far from the actual intent. I will attempt to explain the process that lead me to believe this.
