On-line “church” has virtues, and may be licit in unusual circumstances, but it is not a complete substitute for authentic community that is three dimensional.
Like any on-line thrills, it might have its thrills, but church on line is not fecund. While information sharing can supplement and sustain a relationship formed by “being there,” true sacramental sharing can only come when body and flesh are there. It is the universal experience of the church over the centuries that only this relationship an produce true spiritual children. There is a reason that the local bishop is more central to the life of the local church than any remote pope or denominational head quarters. He brings the Word in a body to the people of God.
My strong bias is toward the local, small, geographically determined local parish where people live in authentic community. It is hard to live in such a community, often uncomfortable, but I have found it transformational. Much good is done by on-line ministry, and even by on-line churches, but that does mean they should ever become normative.
One particularly bad argument in favor of “on-line church” is the notion that a message on-line is the equivalent to a Pauline letter. This argument is bad on three grounds.
First, Paul wanted to be with his children. In most cases (Romans being an exception), he was sustaining relationships that he had formed in the flesh. Even in the case of Romans his letter can be viewed as an introduction for future on the ground ministry.
Second, an ancient letter was more a piece of local theater than an on-line sermon. Paul’s letters would have been read in each local church (they were often directed to a community of believers.) He was not, therefore, the only performer on the Lord’s Day. The local reader would have been able to interpret Paul’s words and change the emphasis, even assuming he did not edit them when reading. Anyone with experience in reader’s theater knows the difference.
Paul’s letters functioned more like scripts mailed to local communities than like on-line sermons. The local voice was present in a way not true of the on-line church experience.
Finally, the letter was read within a local community. In that sense, it was more like watching a movie with fan boys than watching a sermon on a computer screen in your living room. A congregation changes the experience. Anyone who has attended a Star Trek or Star Wars film on opening day and then gone a few weeks later knows the difference between a piece of art viewed by cult followers and one viewed with casual fans. A film viewed alone is another thing altogether.
In short, the use of letters in the early church is a poor justification for doing church totally on-line in all but extraordinary circumstances. Of course, there are better arguments, but this common one should be abandoned.