I have always deeply appreciated @9Marks , but for the life of me I cannot understand why they are drawing a line that would exclude the Jerusalem church in Acts 2-7. It considered itself one church, but had up to and maybe more than 10,000 people, and they met in many sites.

Furthermore, this was the model followed in the early church, IE, the church in Rome as the greetings in Romans 16 express. Any theology of church that would push these churches outside of the definition of church is problematic. Just sayin.